Mint And Proof Sets To Complete Collections, Yes/No

At one of the many coin shows I go to there is a husband and wife with a few tables. The wife sells jewlery and the husband sells coins. About 75% of the coins they sell are proofs and most of the rest are Uncirculated. Getting to know them I found that what they do every year is buy many, many proof and uncirc sets from the mint, break them all open and sell in 2x2 flips separately. They have one of the busiest tables at the show all the time and they told me they always almost sell out those proofs. They continuously order more of them if possible. People just don't like doing that themselves so are willing to pay for each one that someone else for breaking out those and selling separately. They are not cheap but so many buy them anyway.