Oh, Savers.
The holy land of theme parties and vintage clothing, mixed in with piles and piles of random stuff.
For vintage t-shirts without the Urban Outfitters price tag, drop a line into the resources at Savers. You can pick anything from dish ware, to hats, to broken electronics at this store (don't ask me why you would want to buy broken or semi-broken appliances).
This place is also my go-to for generic work clothes, like plain t-shirts or Dickey's or whatever. Convenient and conveniently cool, if you look hard enough.