Both the sportscard and comic book markets started heating up in the 1980s, feeding off one another, so that your average comic shop carried sports cards and vice versa. A lot of this was Mom & Pop stuff, so everybody was learning how each business type worked as they went along, and you tended to value every investment. In the case of cards, you'd typically open up at least one box of a desirable set to see which chase cards you could score to display in a case, and to have common singles to sell or trade to help customers put together sets. Even when you weren't actively making money on those loose cards directly, you provided a service, and by being a resource brought people into the store. Even as the trading card market took a downturn, the rise of collectible card games heightened the value of singles. Game players needed multiple copies of the same useful cards in customizing decks for play, or even just to have enough duplicate cards to maintain multiple active decks for various strategies of gameplay. Just as your Beckett was cooling down, your Scrye was heating up, and games like Magic: The Gathering and Pokémon kept the lights on when other hobby businesses were closing down.
I myself played Overpower and Star Wars, and usually kept my decks in sleeves. Since I was a DC guy, the only box of Overpower that I ever bought for myself was the JLA expansion. Aside from starter packs (basic pre-built decks of first editions,) everything else I got from loose individual packs, or by buying/trading single cards through other players and shops. As was typical, I usually carried my cards in a prefab folded cardboard box that held a single row of cards on their side, and was about 10 inches long with a built-in lid. At the shops I ran and frequented, single cards were usually kept in a variant of these boxes, which I'd guesstimate were something like a foot & a half wide and maybe two feet long. These were more complicated to build, because they would hold multiple rows of cards with separate cardboard slats that were folded into the larger pre-cut template. Cards in these boxes were stood up, and you had a separate folding lid template that could be used to keep dust and debris out of the boxes, or to secure them for transport. That's how you could safely get them to shows/conventions, though being cardboard, you wouldn't want them to be hit with anything more than the lightest of rain sprinkles. At least here in Texas, we'd have stacks of these boxes in our shops, usually supported by wooden shelving behind the counter or in the back room. If you had the right build, you could also get comic book short boxes on those shelves, and because you valued all that stock that you'd put money into, there were often a lot of each type of box around. Of course, in the '90s, after the bottom started to fall out, everybody had overstock to liquidate. You didn't want to pay property taxes on product that wasn't moving. You had to cut your losses at some point, or drown in them.
