Literally one of the best customers of NSO tools is Saudi Arabia (SA), where money literally bursts out of the ground in the form of crude oil. The market cap of Saudi Aramco is 3x that of Apple's. Good luck making it "uneconomical" for SA to exploit iPhones.
I'll even posit that there is literally no reasonable amount where the government of SA cannot afford an exploitation tool. The governments that purchase these tools aren't doing it for shits and giggles. They're doing it because they believe that their targets represent threats to their continued existence.
Think of it this way, if it costs you a trillion dollars to preserve your access to six trillion dollars worth of wealth, would you spend that? I would, in a heartbeat.