The market for the uncut sheets / posters varies wildly. Recently several 1987 sheets all sold for $1, a 1989 sheet sold for over $100 and many of the 1988 sheets didn't sell at all. Below are images swiped from eBay of the sheets that have appeared recently for sale. Of these, only the 1987 Jiffy Pop sheet is actually perforated for the discs to be detached. Unconscionably, Dave Winfield did not appear in that 1987 set.
Recently, I caught a pretty good deal on a lot of oddball Dave Winfield discs and "squares". Here are the regular and "uncut" versions side-by-side.
1983 Roy Rogers - I think this one actually is a pre-production cut, from sheet directly from the printers. I've seen a rolled sheet for sale on eBay. I don't think there was ever an offer of a complete set poster for the Roy Rogers set. These "discs" were actually the lids for soft drink cups. You can see the perforation for the straw to punch through just to the left of Dave's right shoulder.
1985 KAS Potato Chips
According to the Standard Catalog, for both the 1985 KAS and Kitty Clover issues, the squares were from uncut production sheets. There was no mail-in offer for these in 1985.
1985 Kitty Clover
1987 MSA Iced Tea (Baseball Super Stars)
1987 Weis Winners
1988 Jiffy Pop