I was thinking the same thing. Major collectors with large inventories might be your best bet at finding some low grade cards you could get at a discount.
For the earlier series, finding cards with issues on the cheap should be comparatively easy. This reminds me of certain realities of coin collecting, where desirable dates or date runs in certain series are far more common in higher grades than lower, like late date silver before the switch to clad in 1965. Most of what was preserved was pulled shortly after production, thereby not giving those coins much time to circulate and undergo wear and tear. I think the same will prove true for the 16th at least. I would venture to guess that most of the collective 16th inventory in existence consists of near mint, albeit aged and slightly yellowed,cards from packs that weren’t even opened until 20+ years later. So few of us ever saw the 16th in the wild, and we know it was only test-marketed in limited areas.