I shop at the Goodwill and other thrift stores all the time. Yesterday I bought eight placemats for $1.50 and made four (4) casserole carriers as hostess gifts.
We did a plaid block swap and those who didn't have enough different plaids went shopping there and bought men's shirts. You'd be surprised how much fabric you get out of a shirt.
And, since I have a cute new granddaughter I've been buying cute cotton skirts in the adult section, the larger size the better, to make cute little dresses and overalls for her.
I think the clue to shopping at places like this is to look beyond the "real" purpose of the item.