I think turning down more money to go to Saudi indicates he isn't solely motivated by money. This is also corroborated by his turning down the opportunity to join Arsenal and instead joining Wolfsburg previously as he prioritised playing time.
All footballers are motivated by money its why they leave their home countries to come and play in the PL where you usually get paid more than anywhere else, but the facts are here Osimhen has rejected a move to Saudi yet again, after doing so more than 2 times before (one where he signed a new deal with Napoli after winning the titile)
If he was solely motivated by money as you keep saying he would have signed with Al Hilal, he did not agree terms with them and try to renegotiate, as you said.
In any case, it's irrelevant to United because we would only go in for him if we can't sign Gyokeres, which seems increasingly likely we would. What is interesting in Whitwell's latest report actually says Osimhen is actually being revaluated and not ruled out due to wage demands like he was previously