This is going to sound silly but you paid 800k in profits, but now have 4 years of banked costs you can use to _reduce_ your profit margin.

So you pay taxes on 800k profits, but then each subsequent year you reduce you profit by 200k, even though you don't have 200k leaving the door.

If 1M eng salaries was your stable state, then after several years you're... going to have 1M in costs to subtract from your profit! The stable state is the same!

I'm not going to argue about the capex change being "good", I do think it's worth highlighting that for large enough companies you're now looking at a different flavor of tax flow. Amortizing your costs over 5-10 years is something people like doing for other costs after all.