Out of the following reasons, what do you think is the most exciting part of seeing an escort?

When I clicked on this I thought you were going to say that her pictures are real!!! LOL

Other than "D", which doesnt carry too much weight with me, it really is a combo of A, B and C. One you didnt list, is seeing someone over and over, sometimes over many years where trust and rapport is built as that can really lead to better intimacy and the posibbility to explore different avenues with the woman as she gets to know you better and better.
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But I dont want to cop out with my answer, so if pressed, I would say A. That is the initial reason I got into this lifetsyle. I am attracted to women who are generally not attracted to me and I like to play with girls much younger than myself and tbh, I would have no idea how to go about finding them, let alone asking them if I can bed them in the civie world.  
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As much as B and C are imprtant, they fail to match the overiding factor I am still doing this 15+ years later and that is being with a young, chill, gorgeous women who will let me have a total GFE or PSE experience with them, then grab a meal or a few drinks wih them afterward.  
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I hope that is what you are looking for bc it is honest and the best I can do.  

Definitely all of the above.  One is a few times I'm selfish in life at which point I want it to be all about me.  Never found that in dating or marriage, at least long-term

of a boring life.  For me, all of these activities merely become more convenient and less time-consuming when done with providers rather than civvies, but saying they can't be attained without paying is completely false for me.  If you can't do everything with a wife or girlfriend that you can do with a provider, then you picked the wrong woman.   Those of us that came of age during the 70's and 80's (which was pre-HIV) during the heyday of pickup bars (where BOTH men and women went for casual, NSA sex) have already experienced the thrills of bedding a woman you have just met that same day.  The only difference is back then, you didn't have to pay, but your seduction skills had to be good.  For me, TALKING a women into my bed has always been more exciting than buying one.  

ditto

I agree with the Queen and the lovely Scarlett, I thought you were being funny at first and were going to say her photos match her face, LOL  

If I want a young beautiful woman.  Or some specific type that I can't normally get from a relationship.  Or if I'm just up for a girl who has a specific look.

scheduled good or perhaps great sex with a reasonably attractive woman without any drama, an oasis from the real world  . simple and direct.  

...the last portion of "A";     I've had these discussions and arguments before with people on forums like this, and I have watched from the sidelines many of these discussions and debates.      

There is just something about them that makes my motor hum.

Some of these girls I absolutely would have a shot with in real life. Some of them are most definitely out of my league.

I love the fantasy of being with a beautiful woman who is "seemingly"attracted to me. Disclaimer, I was a very late bloomer but now seem to be on the end of many flirtatious advances. I'm not talking about women half my age but maybe 10 to 20 years younger. I can't or won't act due to marital status but seeing a beautiful woman along with the back and forth is so exciting. It's my fantasyland.

I'm not wealthy enough for a girl born in a different century than me to give me a chance.

New Experience Of all kinds

It’s always that one unicorn that stands above the rest.

I just like to connect intimately with girls. It's difficult to do it with just anyone you meet since deeper feelings develop. They calculate whether or not they want it to happen.
Here, it just happens and you move on. Gives you memories you can work with later
I also just like to explore what I like. Dating a girl for 3 years doesn't teach you much about which variety you're into.
There's also a good amount of girls that have a particular aesthetic that I find extremely attractive, but their personality rarely syncs with mine. Getting a taste is sometimes all you need, and there's one way to achieve that in a particularly simple way.

Absolutely brother. Those are the ones that keep me coming back - long term.