I'm sure you realize your LCS gave you a seriously lowball bid at $4 per set. There are sets in that date range that would wholesale in the $4 range, but most are higher. And some are substantially higher. No doubt they'd love to buy the whole lot for $1,600. I would TOO!
Are they in Original Mint Packaging, and complete? Most US Mint Sets will have both P & D Mints, and they often sell for more than their Proof Set counterparts. In both cases, collectors want the packaging to be in nice condition.
Getting more like what they're worth is likely going to cost you some time in research. You'll see there are some that legitimately won't bring you $10, and others that are triple that, and more.
Offhand, you could check for varieties like small date 1960 and 1970-S. Sets with these and other popular varieties have a higher value.
You could post a list with the quantity of sets for each date/type for a guesstimate of the collection's value. If you want to put in the effort, you can check for SOLD prices for each on
ebay (tick that "Sold Items" box). Asking prices are meaningless.
I'll post a couple of lists, but you'll see the values vary widely between them.
https://www.pcgs.com/prices/detail/.../most-activehttps://www.greysheet.com/prices/sp...nt-sets/9551Someone with better advice will offer it. Meanwhile, here's a bump.