When I sold fabric at my garage sale, and at our guild rummage sale, I sold the fabric at $4.00 a yard...most of it was $8.00 or less at the time I purchased it, so basically half of retail. A rummage sale probably won't get anywhere close to what fabric sells for now. I guess you could come up with your offer based on something like the $4 or even less as you woulds be buying it all and helping them out. If you don't want it all, you could resell what you don't want to keep either here on quilt board, posting an ad in your local newspaper, etc.