Business. If they manage to win back to back championships with that lineup then it's definitely worth it. There are so many ways an NBA team/franchise can earn that money back for their organization. You can simply Google or ask any AI like ChatGPT how they're able to afford paying players that much or ask why they’re willing to pay that such amount.
It's not about business. If that's business, they can just let go of him, hunt a good role player on the free agency, or trade him, and follow the original contract. They will have a wide salary cap if they do that, even though they have already granted SGA a max contract.
It's just that Chet is "eligible" on that rookie max contract extension allowed for him
since they got the Championship, that's why his camp asked for it, and OKC approved it without any doubts, since what I mentioned earlier, they want to keep their championship lineup next season.