Curious: What’s your experience like with a $600+ provider and the difference it makes with someone rather than going with someone at $300 and be there twice as long or see 2x over  different days.  

Also, do you prefer to stick with one person or the same few people over time or be with many new providers? And why?

Not meaning any disrespect, but you asked...  

For me it’s not “I have X in my pocket, how do I maximize my hobby?”. Rather, it is “I have not seen a difference that warrants the extra 300/400/500$ per session, so let me find a nice lady whose hourly companionship falls in my comfort range”.

I prefer variety but will repeat (and have) when the connection really happens.

as I have limited funds, but most times that I have splurged, I've been satisfied, (one exception, but that was some years ago).   The lower cost gals are also fun to be with, but it is nice to see a young gal with a pretty face and smoking body who really puts out and makes you feel like a king.

 
As John Arbuckle once said:   You get what you pay for*

 
*Provided you do your homework and research the hell out of the gals before you buy.

 
And yes, I do tend to stick to a passel of gals whom I've come to know and enjoy over the years rather that be a one and done kind of guy.    I like long term relationships.

In my experiences high end per hour $600, are much better than a $200-300 range per hour. Higher ends are usually touring girls and are well put together with hair, make up and lingerie. They are mostly low quantity only see a few screened customers per tour. They have been in the hobby for a while and they like to get repeat business.  
The mid range $200-300 per hour are local girls mostly in it for the money. I’ve been told they get in it for the best way to make quick cash. Do it to support themselves or a habit. While the services are good they just are not high end.  You will leave satisfied but not always completely happy.  
I try to see as many new providers as possible. I like the hunt for a new fresh one or an utr that might be doing this in the short term.  But regs are always good for the convenience and price point to have a go to that is reliable

Ladies in the high end range also stay at 5 star hotels or B and B. They ask you shower before hand and have ample towels and soap available. That is a plus in my book.

In my experience the cost of the visit and the experience of the visit have absolutely nothing to do with each other.  My ATF is a now retired $150 girl.  My worst was experience was a highly reviewed $800 girl.

To me, I wont ever go over $400, and even that is a major stretch and the girl must be offering something I really want.