You fail to mention the two bigger barriers . The aptitude to take risk and the accepting the moral reality. If not for these barriers the market would be flooded with normal everyday girls.
As far as "accepting the moral reality" or else "the market would be flooded with normal everyday girls", during my single days (1980's) the only difference I found between the everyday girls and the pro's was that literally every everyday girl I took out on a date would f**k me for the price of taking her out to dinner*. The only difference between the two as far as I'm concerned is that the everyday girls were less expensive.
* I guess the more moral ones would require a second date.