It cost me ~$700 to do my 25'x25' garage. The only thing I would do different would be to sandblast instead of wasting time with the acid etch stuff. I've got a few bubbles and talking to some cement guys, sandblasting it gives it about a perfect texture for paint.

I also would just count on doing two coats. I did two coats, but there is chips inbetween the coats, then a clear top coat. Looks awesome though. Had my garage been 30X30 it would've cost the same as I had to throw out alot of paint.