The going rate seems to be 350 for a 60 min session.  However, upon going on the models review page, under "cost of service," it will occasionally show a price more than 350 for the 60 min session.  Is the 350 base price just for some of the models?  

You really need to check the provider's ad or web site to understand her pricing and if there are add-on services. But could also be a typo when someone put the price in. Depending on the pool you want to play in 350 is pretty average pricing but you can definitely find some where the average hour is less, and definitely find some where it is substantially higher.

 
So I'm not sure if you're asking about over all trends or a specific provider and differences in prices various clients paid.