I think people tend to think "bargain/inexpensive/cheap" for prices when shopping at garage sales.
Are these fabrics all "quilting type cottons"? These seem to be hot items at garage sales now (at least for me as a shopper)
If you present your fabrics as an opportunity to purchase "unusual, no-longer-available, vintage, or unique" fabrics - rather than "garage sale stuff" - customers might expect to pay more for the items and be willing to do so.
As you may have noticed on the classifieds, fabric is going from being given away - the sender is even paying the postage - to about $10.00 a yard ($2.50 for a fat quarter plus shipping)
You may have noticed photos of "hauls" in the pictures section.
If it was mine, I would save out the pieces I liked - even if I had no plans for them at the time.
I just paid $4.00/yard ($1.00/fat quarter at a garage sale a week ago)
The truly beautiful/unique/good condition fabrics - you could probably get more for them. Haven't quite figured out why, but sometimes folks will buy four fat quarters at $2.50 each and balk at buying a one yard piece for $10.00
I think I would try selling the pieces as yardage first. And then go to the smaller pieces.
If the fabrics are "snobby name brands" - you could maybe start at $6.00 yard and see what happens. It's easier to lower a price than increase it.
The crappy stuff - that could go for $2.00 (or less) a yard.
The really depressing stuff - you could put that in a "free box" - sometimes what one person thinks is undesirable, another person has been looking for.
Just my thoughts on the subject. I realize it's not giving you a "definite" answer.
Good luck with whatever you decide.