Yep, it would make things far clearer. If it was legal they could make their prices public and we would never have any surprise, and we could dismiss all the hagglers and only go with those that are sticking to their publicly advertised prices.
in Japan where it is legal, that is how it works: you know exactly what you will be charged for, for what service, etc.
See this for example:
Service | An independence【 No.1 Gay Men's Escort in Shinjuku, TOKYO 】
EN.HI-NA.COM
An independence ~Best time with Best men~ Foreigners! Tourists!! Welcome!!! An independence is No.1 Male Escort Club for 21 YEARS: serving for...
It is very reasonably priced and guaranteed no tip expected! Just pay exactly what is on the website.