I sent the question from Judy in AR to JudyPete (Whitestone) in a private email because I know she has worked with feedsack fabrics in the past.
Here is JudyPete's reply to me (in an email) and she cautions that it is one quilter's opinion, but that is what was requested. :-)
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"The florals are worth maybe $5+ each, depending on whether or not they are typical or unusual. figurals are worth more. eBay prices are typically less than at quilt shows ... quilt show frenzy sets in.
Light weight sugar sacks with ads are fun for backing mini quilts.
Heavy white "grain bags" are worthless to my way of thinking, but perhaps rug makers use them for punched rugs, etc.
She can search on eBay for current listings but will need to see "sold" or "completed" to get an idea. To my way of thinking selling something for $10 is not worth the effort. eBay and Paypal dig deeply with their fees.
Cut them and use them or swap with someone for some new q shop fabs from their stash."
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So, there is one quilter's opinion for you. Sounds like the plain white ones might be grain bags.
I'll add that perhaps the value if those feed sacks might be greater if you look at them in terms of sentimental keepsakes. If there is no sentimental value, then donate them to Goodwill and let that organization benefit from the sale of the fabrics.
