While I agree he's gone MLS for money if he joins them he also isn't allowed to join Barca for less than a certain percentage of his previous contract, the minimum previous contract is a year too cos La Liga brought in rules to supposedly protect players but it's affected some old players at lessor teams, they have actually been forced to leave La Liga as their wages were crippling the club they played for... Older players usually take massive wage cuts towards the end of their careers but it's being blocked.
La Liga under Tebas have messed up with the rules a player isn't allowed to join a club or renew for less than say 60% of their current deal, the percentage might actually be higher 70% or lower (I'm not sure) but there is defo a set percentage, and with that Barca can't technically afford him in their current financial situation unless they manage to offload a good few players. It wouldn't surprise me if Barca told Messi to accept whoever when joining PSG and that they'll sign him back when his contract is up, if that's the case then they still can't afford Messi and Messi isn't actually allowed to take a gigantic pay cut, not that I'm arsed but the rules are actually preventing him from returning to Barca on a low wage or next to free, he would actually have stayed there once the reality of their situation came to light and very much wanted to take a 90% pay cut.
If it was about the money the biggest contract Messi has had on the table from a European team is from us, the year before he left Barca we offered him the best pay packet of his career and it was more than what PSG offered him too... It also included a crazy salary increase at New York City as well which probably tops this Inter Miami wage if he joins.