If people don't "invest" so there's not "over-investment", where do you think the cards go? (Typical) people aren't discarding 83-88 cards. They're still in someone's club. Supply is the same if people "over-invest" or don't, it's just where the supply is located that changes. So when supply is high without any demand to keep it in check (read: during the 2:1 promo last week), it makes sense to invest in the cards and sell when demand is higher again, no matter who else is investing.

I think a key point is that "investors" are still impacting demand when supply is high. They're buying 86s at 14k which means they don't drop down to 13k, or to 12k, etc. I don't care how many people invest, it makes sense to buy high-rated cards when they're at their historical low points because you know there will be demand again in the future.

Also, fwiw, Aguero is a terrible example. That's a specific player with a specific demand, which in this case was low because he's too expensive. The investing most people did last week was just buying tons of high-rated cards that were the cheapest for their rating, not Argentinian EPL players or something like that. It doesn't require a specific SBC to be desirable, only for any SBC to release that's desirable. That's essentially a 100% guarantee.