Money is irrelevant when you're the richest club in the world. Age is irrelevant when you're the best player in the world and still better than anyone 10 years younger than you. 32 isn't exactly old, plus he's a physical freak and could still be playing at this level in three years, so I'd rather he spend those years at my club than at potential rivals.
Setting the team up around him might not be a good idea long-term, but in three years time we could still be in the exact same position without him and have zero honours, or we could re-sign Ronaldo and win some trophies, then go back to being shit until the next saviour comes along. He could be good for the team anyway. Rashford and co. would probably gain more from playing with an all-time great and winning things than continuing on the path we're on post-Fergie.
Can't see Morata or anyone else having the kind of impact Ronaldo would. Nor can I see any potential big signing sticking around for more than a few years anyway, and only earning a little bit less than Ronaldo, so if he's available then there is really no better option that I can think of. As long as he bangs in a load of goals, which he will, and we win things, which we've a better chance of doing with him than without him, then it's all good imo.