You realize that generally, ladies don't see multiple guys for the same price as a single booking?
Assuming that she charged $300 an hour for a booking, I would expect that having two guys at one would be $600 (two bookings) or more likely, $700 or more since it is a special service (two guys at once).
The ladies aren't like a taxi, you can't "share the ride".
Having said that, if you can find a lady that is willing, you might be able to have a lot of fun this way since it is easier for two guys to please one woman than it is for one guy to please two women at once (as is the more common fantasy). Be interesting to see if anyone else has had any experiences to share trying somehting like this.