I just got through a 2 hour WebEx session where I walked through my deliverable with my client. At $0.33/minute/person for a pay per use session, the bill probably came to around $120 (without integrated voice). That is actually more than the train ticket to get to New York where the client is. Still, when you factor in the time (9 hours of travel round trip!), parking at train station, and (of course) the carbon, it was an economical choice.
An even more economical choice would have been to use Google Doc's presentation feature for free. It would have worked for me because I wasn't showing anything other than slides. If I was demo-ing an application I would have needed to use WebEx or some other real screen sharing application.
Oh well. Something to keep in mind for next time.