I think 150M is our upper limit. But I'm not sure that a Coutinho-transfer makes Griezmann less possible in the summer.
Remember that we went from an expected spending of 80-100M€ this summer to a 33M income - that makes a move for both Coutinho this January and Griezmann this summer financially possible, imo.
I agree it's possible but is it wise? We should keep the balance in the squad, Suarez won't leave next summer for sure and having Messi, Suarez, Griezmann, Coutinho and Dembele could potentially create huge dis-balance in the squad. If we get Coutinho I would rather go for controlling midfielder than Griezmann next summer. None of these players would be willing to sit on the bench and to be fair it would be stupid to bench any of them considering their salaries.
I haven't seen Arthur play but if he is that good it would make much more sense to go for
Coutinho + Arthur or
Griezmann + Arthur than for
Coutinho + Griezmann. We should aim to have competitive well balanced team and not "Harlem Globetrotters show" in the city. I might be wrong but that's my opinion.
Also there is a problem with CB possition if Masche goes to China. This should also be our top priority since we need 4 CB's.