Be a bit more specific, is this going to be a web game, an actual client only on windows? multi-platform client? and also which programming language you'd like it in, so that you can attract the right kind of "programmers".
All payments will be sent by USD.
Why not bitcoins?
Haha, are you serious? Nobody could say, by the time the work was complete, if the BTC would be $30 or $300. USD makes sense.
Well, if they were paid in Bitcoins... at the current Gox price etc. I'd guess that'd be appropriate.