I think Real really needs to sell Vinícius ASAP. His mentality doesn’t suit the club, and honestly, people are starting to dislike Real Madrid even more because of him. There was a rumor about him going to the Saudi Pro League, but that obviously fell through.
They should put Mbappé on the left wing and give young Gonzalo García a chance up front — the team would be much better off that way compared to playing with Vinícius.
They will definitely gain more by selling Vinicus for sure.
Selling Vinicius would be a "smart" move, and not like they would even need to get any new player neither, they can put Mbappe on left, and Endrick on the striker and I bet you that they would still be strong enough to win the league that way. And they can make 150+ million euro from just selling Vinicius as well, so it's all possible.
One thing they are not doing it for, is that it's very hard to sell your best player, and Vini is either their best player or second best if you count Mbappe as best, and selling him would be a very hard deal. They would rather check out and see if they could make it work with him on the field, they would sell him as a last resort. That won't happen this summer, they need to wait one more year for that.