You mentioned/asked "what prices should you ask for the fabrics?"
I think the answer to that depends on several things:
Are you trying to recover the cost of what you spent on the items?
Are you "trying to get rid of it"?
How attached are you to some of the pieces?
What do you think the people are willing to pay? Or more accurately, what would YOU be willing to pay?
(There are some people that think you should pay THEM to take the fabric - - I was at a garage sale yesterday, and the seller had most pieces marked at LESS than $0.50 per yard and she told me that someone had complained that her prices were too high)
My personal opinion - and mine only - is that I consider it "fair/reasonable" to ask for what it would cost to replace a piece with something similar.
Examples: Most VIPs - I think it's reasonable to ask $4 to $7 per yard for them.
Most Hoffmans, Kaufmans, Alexander Henrys - $8 to $11 per yard.
There are exceptions. Right now, Dr. Seuss fabric is frequently going for very high prices on e-bay.
I also think it's fair/reasonable/sensible to recover the out-of-pocket cost of shipping.
What you choose to ask is entirely up to you. When I read the classifieds, it varies from people giving things away (postage included) to asking $5.00 for a 10 x 10 inch square of VIP fabric.