We don't usually leave expensive items, but they're always new.
We find mainly crap in our area-beat up matchbox cars, expired GNC discount card, movie ticket stub, used golf balls, etc. Lots of broken toys and a lot of things that can only be described as someones garbage. (as in they must have retrieved it from the trash)
I don't for one minute think "good" swag has to be expensive, but a gum wrapper or a couple of rubber bands shouldn't be used as trade items in my opinion. Even the least rich among us can no doubt afford a quick trip to Family Dollar.