Salah and Mane have one more season on contract until June 2023, especially Mane who is rumored to be leaving and Bayern as his best port, if Salah follows him to leave can Liverpool replace the duo with other players? I think it's really difficult to do as much as Liverpool can keep one of them, because Liverpool really rose because of the cohesiveness of their striker to become the best in the EPL.
It's hard to imagine if Salah and Mane left.
The good thing for both Salah and Mane is the fact that their contracts will end at the same time hence they can leverage their contracts that way. They will be able to say "pay us more or we both leave" and ask for a lot more. If it was just one of them, you would just keep one and send the other, but in this situation you can't lose both at the same time. So if two of them get together, they could really milk LFC a lot and get a ton of money.
Not saying that they will do that, all I am saying is that there is a chance they could do something like that if they wanted to. And that is something that LFC should fear, wouldn't wanna be like PSG and end up paying too much.