What's a good price on very fine grit sandpaper?

I don't think that is too much... it's a lot cheeper than some of the high quality brands.

I use MicroMesh products a lot, http://www.micro-surface.com/default.cfm?page_id=1 and they are about $10 per 12X12 sheet. BUt they are soft cloth.

The thing to check on is how much grit comes loose on your work while sanding it.

naplak Modeling
naplak.com/modeling

Amazon has great deals on assortments, pre cut in various grit selections. A real deal.