I agree with what's been said. Less stigma=more workers=increased labor competition=lowered earnings. This process can be seen with what has happened in strip clubs around the country since the 1980s. I know in San Francisco in particular, many more people found it acceptable to work in clubs, and this greatly facilitated the introduction of not only stage fees but also lap dances and eventually outright prostitution in the strip clubs (whatever one thinks of lap dances and paid sex in the clubs - and I think it's a complex issue - at the time these changes amounted to a management-imposed "factory speed-up" for the workers there).

The money for sex work might still make it an attractive option for many people - I agree that not everyone would rush to become a sex worker, and that it would still pay more than many other forms of service or professionalized labor - but how could the end of stigma and of criminalization not make it a more attractive option and thereby lower the earnings?