That's the problem. Other clubs (sheik or state-owned or whatever, idea is some dude with many billions owns the club) can afford flops amounting to 200-300m. We can't. That money has to be covered somehow by what the club generates.
I'm sure Bayern could spend 150m on a player if they want, but the risk is deemed too great, and pointless in the end. It's a business decision. You have to justify that spending with clear reasons, not pipe dreams.
How do you justify 300m spent on Coutinho and Dembele? Was either of them a World Cup winner or something? Were they golden boot winners, verified in CL by scoring in semifinals, final and such?
I think even Haaland is a risk for a huge sum. The only one who isn't a risk for 150m is Mbappe.