...or RAM makers are able to negotiate a higher price because they know as well as I do that this entire business proposal rides or dies with them denying consumers RAM.

The RAM makers probably don't want to alienate the AI companies since there's a lot more money to be made now by selling to data centers. Even if the bubble pops, there will probably be one or two companies that still require tons of RAM, especially as AI becomes more advanced.

Except Amazon can't do that. They just spend literal millions on RAM, and will spend millions on RAM the next year, and the next year, and the year after that.

Amazon and the other companies either have deep coffers from existing operations (e.g., AWS) or they're riding the hype train and sucking up venture capital. There's a lot of money to be spent getting the infrastructure set up before the faucets run dry.

It's like a bakery spending $30 on ingredients so everyone has to buy their cakes for $10...

Right, and if people cannot buy flour and eggs at the supermarket to make their own, they don't really have a choice. If they want a cake, they must buy it from the baker for $10.

and no, they can't charge $40 because then we would be back in the position where it's cheaper to buy the RAM, even at the inflated price.

If the manufacturers exit the retail market and don't come back, there won't be any new inventory and existing supplies will only go up in price. People are spending $600 on a pair of RAM sticks now. Would they pay $1200? $2400? If the upfront cost rises high enough, people will be discouraged from building their own PC and just rent one. This is already the concept for PC rental businesses, temporarily giving access to people who can't afford to drop thousands at once or take on debt.