If that happens and Liverpool really wants Takefusa Kubo from Real Sociedad to bring him to Anfield, I will be very happy and looking forward to that happening, and the rumors I read are that Liverpool will have to spend a very high amount of money if that deal happens. Takefusa Kubo is a good player and he is still very young, with the talent he has Liverpool can maximize and use it well,
And if this really happens, Takefusa Kubo will adapt well considering that he has a compatriot at Liverpool, namely Wataru Endo, who he can take advantage of. What is clear is that this is Arne Slot's first recruitment after becoming Liverpool coach, if it is true the deal will happen and it is not just a rumor
That could actually be a good replacement for Salah without a doubt. He is not as good as Salah compared to their peaks, but he could be better than Salah right now, or at least in a year or so. They should definitely consider this deal, could be something that they can benefit without a doubt.
I think the most important part of this situation is that he is only 23 years old, which means that if they buy him now, they can play him for another decade, and when you find players like that, you should try to get them for whatever price you can. He isn't going to be cheap though, and if the offer comes from Liverpool, they will definitely would want some extra premium on it, and that is why I think something like 70-80 is possible, or at least that is what Sociedad would aim at, that would be their hope. If they get Kubo somehow, Slot would have a good first year, they will have a good rebuilding phase, and they should be capable of doing fine on the long run too.
Not saying they will win the title, but they won't get too far away from it neither, and that's what matters for a new manager. With City and Arsenal fighting for top spot, if they can finish third that would be good enough.