I expect a GPT-5 training cluster to cost $10b (Say 100k blackwell chips + associated infrastructure), and a GPT-6 capable cluster to cost $100b.
It sounds like a lot, but its just a typical mega-infrastructure funding. The Californian high speed rail is also around $100b for example, and Microsoft has $90b in cash reserves.
The gulf states are also dogpiling in AI, because they finally see a true viable alternative to oil: renting out GPU clusters. Just swapping to renewables is not enough, as their economies is predicated on having a huge, simple, defendable profit source that is exportable. Now they can redeploy the spare oil money to a use case, that has predictable demand, extremely capital intensive, and far more productive than building new cities in the desert.
The world in the end built $trillions in value of power stations and roads. I expect the same for data centers, having entire farms being replaced by humming GPU racks. But that will take many decades.