I would agree with previous post in that the two markets are operating on similar , some the same , but still key different fundamentals.
No one is rushing to buy PSA 9/10 WOTC/EX era cards as investments because their favourite YouTuber showed them a price chart of prices moving up 10% with an open mouth thumbnail.
The one big factor in my opinion that people tend to somewhat know but not really consider , especially the younger crowd, is that WOTC/vintage has had 20+ years for supply to flush out. Though for most of this time many cards were not worth grading even in PSA 9s.
It’s really 2019-2021 that flushed a lot of the supply out, as a result I do believe the prices are being suppressed where the supply has been able to cater for demand for the last few years. I do believe we will reach a point soon where there will be small supply increases moving forward and the demand will begin to overtake the supply.
if you look at grading rates of wotc / vintage era , you are seeing significant slow downs in PSA 10s and 9s, even with CGCs impact. You can see the price movements in gold stars , shinings over the past year.
As a result the prices are drifting up , you could say it’s being pulled by modern too, which is true however when most social media channels like YouTube post content, I can’t remember the last time I saw a recommendation / post on buying a WOTC PSA 9 1st edition holo, or an EX. Yet the prices are holding / have drifted up over the last year.
I can’t speak for everyone but to generalise - as a primarily vintage collector , I buy PSA 9s mainly or raw then grade, there are very few circumstances that will result in me needing to sell any of my collection as I am well into a career with a house etc . Can the same be said for someone buying a moonbreon for $2k today? Almost Everyone I see picking these up are buying for investment , flip, it’s the cool thing purposes.
In a nutshell - supply of everything was high for the last few years but Moderns demand was insane vs vintage somewhat “normal”, however its vintage’s new supply of graded cards that will begin to crater and that’s when you’ll see the steady increase.
so is vintage undervalued against modern ? The market prices things wrong all the time. Only time will tell.