Slabonomics
I have collected all four (PSA, SGC, BVG, GAI) types of slabs for over 10 years in prewar cards.
I have sold all four types of slabs as well. On average I have held cards for five years.
GAI - I only had 20 of these. Before selling any of them, I cracked and submitted them to SGC. They all graded, albeit a bit lower. I have sold half of them, but when they are all sold, I will be in the black easily, because I paid less for the GAIs to begin with.
BVG, SGC & PSA - have all netted me the same percentage ROI. BVGs are a bit cheaper than SGCs on the buy side, and therefore sell for a bit less on the sell side. Similarly SGCs are a bit cheaper than PSAs on the buy side, and therefore sell for a bit less on the sell side.
At least for me, slab diversity has had "no" economic consequences. I am a collector and not a dealer. I try not to overpay or oversell. I am not truly a buy the card not the holder type of guy though, because the holder and the grade do affect what I am willing to pay, and consequently what I am willing to sell for.
The disparity in slab pricing does increase "exponentially" in higher grade and lower pop cards. The effect of the PSA Registry on pricing of high end cards is very real, but in mid and lower graded cards, the difference is manageable for me.
So I buy cards that I like or want at reasonable prices, but never exclude a card from my consideration based on the type of slab. My OCD is focused not on a particular "look" or on a "Registry" position, but rather on a sustainable, yet changing, collection that will hopefully never result in red ink long term. Nor do I expect to become wealthy because of my cardboard.
Sorry, no punch line.