I tell DH right away, but then I take him to the computer and show him that I'm selling on the QB the fabrics that I can live without, so I can keep the ones I love for free. That does make him happy - especially when I show him my sale, "see here's the last Paypal payment that reimburses me every dime. Now I can either keep the rest, because it's free or sell a bit more and get enough money to go back and do this again." He usually says "sell a little more, so you can go back again. That way he knows it won't cost him next time around either. Try it! It works! (And of course, we all win@!)
p.s. my Goodwill's around here never have any great finds like that.