I'd figure maybe $5 to $10 a huge garbage bag as a starting price...depending on the content. A bag full of big pieces of LSQ fabric is worth more then a bag full of cheesy scraps. And it also depends on your area. How much do your thrift stores get for fabric? Do you do yard or estate sales? How much do they ask. Check the closest Craig's List and see if you can find any sales to give you an idea. The bottom line is what can you afford, do you need it and you can always hit the yard sale and see how she's priced it then and make her an offer! Have fun, it sounds like a great situation!