It seems funny to call the software our conference runs on a "platform" as that sounds very "enterprisey" and official. In the past we've done aspConf and mvcConf with sponsors who helped pay for things. We used Channel 9 and had a studio and streamed either from Seattle or using Live Meeting.
However, this year we wanted to do it on the cheap and more distributed. We wanted speakers from ALL over in all time zones. How cheap? About USD$10ish we figure. I'll get a complete bill later, but we basically wanted to scale up, do the talks and scale down.