I honestly don’t think Messi cares all that much about his wages. He’s set for life. Just getting the opportunity to play with best-mate Agüero, for Pep and the management team he seem to appreciate is a great solution for his final years as a footballer. I could see Messi matching Agüeros wages.
And given everything Messi has done for Barcelona, if they forced him to stay, they’d be the most hated club in the world. I think they could let him leave, but who knows, their management is a joke.
That is the only way I can see it working. I mean he is 33 after all, 2/3 years with Aguero before they retire together at the best club in the world would be incredible.