The guy I can recommend is not in Buenos Aires anymore, but in Cordoba, a beautiful mediterranean city. If you happen to be around, you should contact Joel:
http://ilikepinga.com/2017/07/22/joel/
About fees, I have not been there in two years and there is a lot of inflation. Two years ago, a top tier escort from soytuyo.com would charge the equivalent to U$S 35 for an outcall. Just be aware that I can pass for a local, I am not sure whether or not they have a different price for foreigners, specially Americans. I am 99% confident they do. You should not pay more than the equivalent to 50 bucks.