I think there's a $195 setup fee and then $20 per month.
You can't download extended historical data via the API, plus they will question you what you want to use it for, so you don't use too much data. They don't give entitlements to just anyone.
If you develop a commercial app to use the API, before distributing it you must pay them $2500 in addition.
You can get streaming live ticks by using a .Net DLL they have, without the API. I tried it once and it worked, but it's not easy to use. Can't remember the details of how i hacked that out at the moment, though. I just did it for fun, but i don't use the API any more.