I charge high. But I donated to a Tricky Tray (raffle auction), so people were purchasing raffle tickets for a baby quilt.
Are the contributions tax-deductible for the purchaser? If yes, you can charge a little more for things (think PBS and their fundraising).
think about what an upscale boutique in your neighborhood would charge for this, and price it similarly. You may also want to put a sign in the booth "made by local fiber artist Your Name" to help justify the non-thrift store price for the items.