I would think valuable cards are more likely to be slabbed than those where it makes no economic sense to do so, so I'd wager the ratio of slabbed/unslabbed high numbers is different than the ratio for the low numbers. 9,000 high numbers available per card seem high to me; if there were that many I have to think prices would not be what they are, although I think there are more highs out there than their prices warrant.
If you assume something like 10% of highs are slabbed you get something like 1,800 available per card, which seems more realistic. Plus you have SGC, Beckett adding a little to the total so maybe 2,000 of each existing using that math. The problem of course is you don't know how many raw highs exist.
How many people actually collect vintage and of them how many do the 52's is another number you want to work out. Plus the grading of stars like Mantle and Mathews skews things.
