Coins are typically not a good investment. There you go, both words in the same sentence, and I don't see anything wrong with it.
It’s too difficult to get what the mint asked or more in the aftermarket for most. The bids in the sheet aren’t advancing. Put your money in gold and silver close to melt or 19th century type, and CC coins. I have done well with low pop World Gold issues. Mods basically dead.
I learned about investing in coins from a wise old sage who said "The dealer who is trying to sell you coins for investment purposes - ask him what coins he is buying for investment purposes. An honest dealer will tell you only the truly rare ones" I buy the proof sets from the Mint simply to break them open and put them in my collection sets. Some non-silver proof sets are selling for less than the original OGP price! So the short answer to this rather long essay is don't buy proof sets for investment purposes!