Around $400 per session, depending on who does it, my girl is a PA. PAs or docs are usually more expensive. Laser centers with certified technicians are usually a little cheaper.
For Aeron--
some places charge by time, like the person you talked to, and some places will charge you a set price per "session". I'm not certain, but I have a feeling that the costs would ultimately equal out-- if you pay $400 all the time, regardless of how much growth, you are getting your money's worth for the first few sessions but as you have less and less hair, there won't be as much to zap, and it won't take as long, so you're sort of "overpaying" at the end. A place that charges by time will be more expensive for the first few sessions, and get progressively cheaper as all you need are touchups. Hope that helps.