I have done garage sales in the past and know how much work they are. When I go to one, I usually pay whatever the item is priced because of this unless I feel like the item is really overpriced.
I keep a tote bag in the living room (usually one of the "freebies" I have acquired along the way) and as I find items that I no longer want, add them to the bag. When it is full, I take it to the local thrift store.