This is not 'Nam. This is the Premier League. There are rules.
Chelsea took a pretty hefty loss last year. They can expect to get about half of it back from adding gate receipts back in. Since they were making money pre-COVID, I would imagine that they're fine under the Prem's sustainability rules right now. If they're amortizing the present purchases over longer (5-6 year) contracts, they can probably stay fine as long as the owner makes up the resulting losses out of his own pocket up to the cap. They're going to be sell-to-buy for a few years, but otherwise this works.
Double that outlay, and the math quits working unless they start selling players. They would be committing to selling a major player every year to stay compliant, and more to make any signings. We all know how well that need worked out for us this summer.
The wild card is exactly how UEFA's replacement system for FFP, with the even less attractive acronym of FSCLR, will work. If Chelsea doesn't have to amortize transfer fees under those rules, and can effectively write them off now, spending half a billion is a way to end-run the transition period from FFP to FSCLR. If they do have to amortize, which they probably do, there is just no way that they can get down to wages plus the amortization on a half billion in transfers being under 70% of revenue three years from now without a fire sale every year. Their pre-COVID wage bill was already 75%, and they have to pay these new signings, who will largely be crowding out players on lower wages.
Spending that much right now, if they have to amortize, would be tantamount to Todd Boehly having to be Wayne Huizenga conducting the infamous Florida Marlins fire sale every year for several years, most likely starting two years from now. The best part is that they couldn't even do what Barcelona did and sell assets other than players to comply, because proceeds from such sales go on a P&L but are not considered revenue.