Hi Jake -- You can read our somewhat unflattering description of US proof and mint sets on this CoinQuest page. These sets make nice gifts and nice collectibles, especially for young people who may become interested in coin collecting, but don't expect the sets to be worth very much. This is true for your modern bicentennail 3-coin set.
The Grey Sheet, a conservative price guide for US coins, lists the catalog value of perfect and pristine 1976 3-coin sets at $17 US dollars. Perhaps when James Kirk is captain of the USS Enterprise in the 23rd century, these sets will be valuable. Until then, keep them as collectibles, not as investments.