Like I said in another thread, there is money to be made for Haland. It all depends on Laporta's, and to some extent Koeman's, ability to convince players to leave.
Lenglet, Firpo, Dembele, Puig, Braithwaite could get us close to 100m, give or take. All expandable players. If not enough, we could also try to sell Roberto, Trincao who still have some semblance of value. Youth players like Collado too.
On the other hand I do have a hard time believing we can sell the likes of Griezmann, Coutinho, Umtiti or Pjanic. Best we can do is getting them to leave on loan while paying a part of their wages.
Bring in Alaba, Gaya, Garcia, Depay, Emerson for 25m or whatever they cost, sign Messi for 2 years 30m/year, use everything else to go in all in for Haland. Improve both wage structure and quality.
We'd still be short one world class CB though. If Messi doesn't renew use the funds to buy one.