I wouldn't worry about Vinicius because he seems to be willing to be bought by clubs in the Saudi league.
https://talksport.com/football/3388563/real-madrid-transfer-news-saudi-pro-league-vinicius-jr/Of course 350 million for Vinicius is a lot, but if we remember what money the Saudi league spends on players every year, I think that finding 300 million for them is quite realistic and Vinicius will probably get 3-5 times more than in the real and this is probably the minimum.
I think if Saudis are ready to spend such money, then Vinicius and Real should agree, because with the kind of game Vinicius is showing now, he will soon have to sit on the bench, unless of course Alonso wants to lose matches.
I was about to ask if you really believe this but they are so crazy over there that it could really be that they could pay >300 million for a player. Is Vini Jr. worth that amount? No way, but I'm sure the Saudis want him.
If I were Real, I wouldn't think twice about that amount and sell immediately, regardless of which player they want. In my opinion, Vini in particular is expendable and easy to replace. There was CR7 before him and if you could replace a prime CR7, you can replace Vini 100 times over.
After buying Neymar for 220millions any transfers seem realistic now.
300 million of course is a huge amount, but Vinicius almost got the golden ball and was one of the most important players at Real Madrid, so he is a stellar and productive player.
For Real it will be just a gift of fate and I think he will gladly let Vinicius go. The only problem may be Vinicius' desire to play in Europe, because now he is 25 years old and this is the best and most productive period for the player and Vinicius may want to win more trophies in Europe, but I think Alonso is not very satisfied with his game now and may just put him on the bench.