My collection is a pretty extreme example of the type where the value comes from volume and/or scarcity, and not from a smaller number of ultrapopular and spectacular individual cards, which I have never really gone in for (sometimes to my later regret...)
As a prewar set collector whenever possible, I haven't closely followed the huge price spikes of PSA 8+ rookies and Cobbs and so on (although I'm generally aware of them).
So it's important to understand that my comments below don't apply to cards that have been seeing wild spikes up and down that amount to many thousands of dollars.
Anyway FWIW, in preparation for selling some stuff from my collection, and buying other things, in the past few months I've spent a LOT of time buried in VCP looking at sales of prewar commons and stars (as opposed to the dozen or so players that the hobby treats as superstars). Mostly in grades between 2 and 5.
This is the pattern that I've seen again and again and again:
Mostly flat prices across the whole of prewar for several years through the winter of 2020, and then an ominous dip in March and April where some stuff went for peanuts because people were too distracted to buy. Then in early summer you can trace the start of a meteoric rise in prices, again across most of the prewar world (the chunk that I've looked at, anyway). Commons, stars, low grade and high grade, it all goes up for the rest of 2020 and most of 2021.
You can trace the pattern, too - go to VCP and look for non-Ruth-level prewar cards that sell a few times a year - especially the type of cards that go for between $50 and $500 in PSA 2-4 condition. You'll see it happen through 2020 and 2021, sometimes continuing up to the present-
In the two years after the beginning of 2020, I estimate about 100 percent increase in that category of card. Obviously that's a rough average and most examples won't precisely follow that pattern, but this gives you the outline as I've traced it.
Since 2022 it seems more varied. Some prewar sets, especially CJs and M101-4/5s and tough postcards seem to continue going up. Others like T206s and T209s and Cobbs have gone flat or even come down some - probably they were ones that shot up too high too fast, and required some degree of correction relative to their rarity and demand.
But the drops are exceptional cases. Most cards in most sets still seem to be stable or still rising, now at least twice their 2019 value, sometimes more like thrice.
So I would guess that anyone who has a prewar collection like mine - with the average value in the low hundreds per card- will discover that their whole collection is worth at least twice as much as it was in early 2020. Which seems like a good thing if you're selling off - less so if you're selling to raise money to buy new stuff like me
