This has happened to me many times now. I see a LOCAL young hottie favorite me. I figure she is interested so I send her a message. It is very basic, nothing explicit or graphic, like, “Thanks for favoriting me. I am looking for a mutually beneficial arrangement that can turn into long term if we click. Let me know if you are interested.” Most of the time, they just turn radio silent after reading my messages. WTF? Can anyone explain? I get favorited by tons of out-of-towners and I figure most of them are just scammers, but locals?

it's the hot babe MO: favor everyone, and I mean everyone...and of course, they all bite - which give the hottie a choice.
My strategy is simply to wait a few weeks until all the flakes/fakes have exhausted her and then respond.

I agree and a lot of them don’t even view your profile. I never contact anyone local that favors me without even looking at my profile. I never contact the ones from out of town, even if they view my profile unless they say they are coming to my town which they do from time to time, especially around the holidays.

(In Maxwell Smart voice): The old favorite-without-viewing-your-profile trick.

I never message ANY ladies first! And i mean zero. Noda! Because if i chase them first, 99.9 percent of the time they don't respond. Yes, i said that. I watch who favorites me and hope they message me first. That way I'm now in the position of power. Hate to say it, but, these young ladies are very skiddish. They've had their fill of stalkers, and pervs..when they come to me my arrangements with them work better..seriously. gotta keep in mind guys, you're now a hellava catch..because you're percieved by them as rich successful men, and to these hotties that equates to u having extreme confidence as well witch is just down right sexy to them. In otherwords, your status is equal now to their beauty because of that..dont chase guys, let them come to you..

I was having lunch with a truly beautiful 18 yo possible last week.  She's not just "model material" she's actually a model who already has one fashion magazine cover shoot to her credit. Anyway, she told me that 6 hours after she put up her profile she had 50 messages in her inbox!  She replied to 4, and chose me to meet for lunch. If you want replies, you have to write something creative and engaging that is unique and sets you apart from the rest.  In other words, you need to raise your game.

Despite all the crap SA self-promotes about the extremely high women:men ratio, in fact if you only take the less than 1 day active members it's about equal.

Oh crap pole position, no wonder the attention to me has dropped? Lol guess it's time to hit the "net worth B.S. button again to the next level??

I'm sure some are inundated, but you can see the gals who are on there week after week.  Apparently they all aren't hitting pay dirt.  Some have start dates that go back months or years.  

Here's how I go about this:  
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1. I never message 1st - unless I am travelling to another city for at least 3 days. Then I'll blanket 10-15 POT's in that area a couple of weeks before I go to try to get 1-2 M&G's set up.  
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2. I may favorite a POT if she is especially hot and has been a member for a while, but I will still wait for her to message me or favorite me back.  
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3. I usually set my account to notify POT's when I view them and when I favorite them.  This shows some interest, and I hope will result in reading my profile and a message. Note: I actually understate my annual and net worth on my profile. The idea is to attract SB's who are interested in a "connection" at least as much as (but never more than! lol) the sugar. It also helps in the sugar negotiations later. It's hard to say your budget won't accommodate $800 ppm when you claim to be making a cool million every year.  
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4. Important: If I get a message (85% of the time it's the ubiquitous "Hi."), and she is local, and meets my other criteria,  I will always respond with a question, usually relating to something on her profile. Note that I have a line at the end of my profile that says "I respond to all messages from people who are local to me."  
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The question approach does a couple of things:  
First, it shows that I read her profile - implying I am actually interested in "who she is as person", blah, blah, blah.  
Second, it asks her to talk about something very important to her - namely HER. Women (and men) love to talk about themselves, it's the single topic they know the most about and the most important them. So let her chat believing I am interested in the real person behind the profile.
BTW: This tends to sort out the scammers and semi-pros very quickly. These types will generally NOT answer my question and instead will respond with budget asks and requests to meet NOW.  
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5. I usually don't favorite newbies as they are generally inundated and overwhelmed with one-liners from lots of guys. I prefer to give her at least a week to sort through the fog and get a better idea that she ain't gonna find Richard Gere (if she's even seen that movie!) and she can start to sniff out the creeps as well.  
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6. If I get past the 1st message and 1st response, I generally continue to use the "question" approach with follow up questions and asking her about her arrangement experiences and expectations. I'll also answer her questions (as honestly as I'm comfortable with) and start to insert hints (or just ask) about meeting soon.  
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7. If we seem to be progressing, I'll try to move the chat off SA and onto text.  Text means we can discuss details about sugar and possible BCD, and it let's me do some additional vetting of her to screen scammers and catfishers. If she's only willing to message through SA (or KIK, what's app, or other anonymous chat app), I'm less interested as those scenarios tend to have a much higher NCNS rate on the M&G (like 65%!).  
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8. Callout for Porn Star SB's: As I am in the Los Angeles area, I will be more proactive (favs and 1st messages) with selected porn stars in the area - especially "newer" ones and porn stars that also escort. I have been rather successful in this and have had 4 arrangements over the last 2 years, with 2 still active. Interestingly, local porn stars who sugar are generally willing to take less sugar and spend more time with me than their escort rates (if any) and they are happy to introduce me to their porn star friends for 3somes or as additional SB's.  Life is good.

a public profile pic? Are these what reel in the messages from the POTs, or is it the text in the profile once read?

I think for the younger babes, it's everything, as many of them apparently don't read the profile!
Did want to supplement my previous post by saying when she views Favorites the Age/Net Worth demographics appear, for messaging she can see the first line, which as we discussed before, is often all she needs.

Pretty sure there is ample evidence (at least according to SA and every other "dating" site) that a profile pic is THE most important factor in getting a connection.  It certainly is for me. I don't read profiles without pics and I rarely respond to messages unless she proactively gave me access to private pics 1st. If I can't see her I can't know if I'd want to bang her.  If I don't want to bang her - end of story. I'm not here to give charity donations to millennials.  
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In the context of the sugar bowl, I would think that a POT SB first will need to decide if she's willing to fuck you before she will talk to you. I'd be very worried by 1st contact messages with no SD pic that she's a pro, semi-pro, or  scammer. These three types are much less concerned about your looks as they just want access to your cash with little (or no in the case of scammers) actual face to face time, let alone BCD time.  
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As to your strategy, you will need to see what works best for you. But understand that a POT SB will only be able to use the info you provide to decide if she wants to talk to you, let alone fuck your brains out. If that's just your salary and net worth, then that's how she will evaluate you. If you want her to "know who you are" then write a decent profile with insights into your personality and values. In other words, give her what you think will most likely "sell" you to her as the perfect SD.

requesting to see their private photos?  Not really a message, but maybe an indication of interest?

which I easily believe.
Girl (who's about a TER 8+) said she had 400 unanswered messages and 2300 favorites!
She was probably responsible for many of them, but just puts in perspective what the hotter girls get.
She made mention of the [false] premise that women outnumber men by a lot on SA, and was somewhat confused with her situation.