I hate thieves! I would have gone to them and let them know they needed to put it back on the table or pay for it. Also, I would have said it in a loud voice so everyone in the driveway/garage would hear it! If you steal, you deserve to be embarrased.
I think your prices for good quilting quality fabric is fair - I would have bought it. I might have asked for a little discount if I purchased a large amount. I always love to buy books for $2 or $3 each - they are so expensive new that I think any price that is less than 75% is fair. We all get those 40% coupons in the mail for brand new books so I never want to pay more than I would with a coupon at the store.