That's a stiff order in RA. Because of the high demand, limited number of boats and resorts, and the fact that it's "way out there" from almost anywhere, it doesn't come cheap. You're looking for dive prices more common in Philippines or Thailand.
Here's a boat we've been aboard before in N. Sulawesi, and we'll be aboard her again in RA in 2012. I highly recommmend this operation. No AC (cross ventilation since all cabins are on deck), no hot water (call it almost lukewarm), but spotless, well-maintained, excellent crew/guides, and a lot of fun.
Diving Indonesia with Wallacea Liveaboard : Togian Islands & Banggai - after Manado, Bunaken and Lembeh Strait
There are a few boats that are essentially "camping on the water," dorm-style bunks and shared heads/showers, but they're hard to find in a web search. I've run across them before, but haven't logged the websites. Good luck!
