Yeah so that is one of the possibilities, people start making their own shovels. There are a bunch of others: People start getting shovels from somewhere else

Yeah so that is one of the possibilities, people start making their own shovels. There are a bunch of others: People start getting shovels from somewhere else even if they aren't quite as good (AMD). They realise there is actually only a small group of them buying literally all the shovels and they use that position to force more favourable pricing. Another company works out how to make a better shovel, or worse something that isn't even a shovel anymore and is much more efficient at mining. (These don't exist for training yet but there are inference chips that make NVidia look terrible in comparison) etc. The fact of the matter is that it's not a stable situation, something has to give. Hype can allow these sorts of massive imbalances to exist for short periods but there is always balance in the end.