On TER, the main escort review website, my scores range from an 8 to a 10 depending on taste; I think the lowest I've ever had was a 7 from a guy who was exceedingly upset that I was at least a foot taller than him. I'm not exactly an amazon, though, just leggy. As I mentioned before, I get compared to Audrey Hepburn a lot, since my coloring is quite similar.
What makes me more desireable? The question is more "What makes me different." Many people would call the Playboy "blonde, tan, and buxom" look extremely desireable, but there are a lot of escorts with that look. I'm pale, brunette and slender with smallish boobs; I wear rather minimal makeup and don't have any weird piercings. Additionally, I'm intellectual shading to geeky, I can discuss Shakespeare, non-contemporary music, and politics with a reasonable amount of aplomb, and I make it very clear that prefer books as presents over flowers or chocolates. Basically, I don't look or behave like most other women in the business, so I get plenty of niche customers.
Plus, I give awesome head and can have multiple orgasms. Those are also big factors.