Money can always be or become a goal again, that is very relative. From a political or moral perspective, I don't understand why Ronaldo went to Saudi Arabia and play in a country where human rights are worth shit. From a financial standpoint, he must be absolutely crazy to deny an offer where he can earn in 2.5 years what he has earned in 20 years before that. It is so much money that it becomes relevant again. If someone offered Elon Musk 10x of his net worth for Tesla, I am not sure what he would do. It is always relative. We normal human beings would think that at some point enough is enough, but that's perhaps not how it works.
It remains to be seen how Messi will decide as I am really interested in his decision and whether he has the guts to decline an offer paying him 400 million a year. Does he need the money? No. But that's not the point.
I think there is a difference between that much money. When you made 500 million dollars in 20 years, and someone offers you 500 for 2.5 years, that is still "millions", even though it is more money than we could ever make, that's as much as someone who owns like a few dozen wind turbines.
Imagine being the richest football player, and "maybe" even the greatest football player ever lived, and you have as much as someone who has a good business, it is not really that crazy, we have about 500 or so people, maybe more, richer than him because business makes a lot more money than sports at the top, richest sports people can't compete with richest business owners. Elon on the other hand has so much that offering 10x can't be even done.