Last home stand they had items on sale racks around the 300 level. The deals weren't that great though, the stuff was a little over priced rather than a lot over priced.
The hats sold outside of the ballpark are cheap, but obviously not high quality stuff.
Not many bargains at the ballpark. Except for food, you can get cheap eats at the push carts outside the park and carry them in, Rocklands is also outside the park, for the kid they have cheap hot dogs at the stand right by the playground area.