The way I see it Salah has already repaid his transfer fee and then some. Gone are the days when he would burst past opponents, or leave everyone in the dust on the counter, but let's see how he does in a new setup. Slot seems to prefer all the precise passing in and around the box and we saw enough of Salah last season to know he can adapt to that. As has been rightly said, he would have a tonne more assists if Nunez didn't spectacularly lose all his sight and coordination near the goal.
There is a middle ground in which we offer short-term extensions that suit both parties and we can pragmatically part ways at the end of it by offering wages linked to future predicted output. Most sensible fans would want a reliable source of goals at the club before Salah eventually departs whenever that may. The boat of selling him for huge money (if there ever was) has long since sailed, so now it's about cautious pragmatism until someone either a) comes in) or b) steps up to produce the numbers we need. He will surely get the big pay at Saudi someday but he won't want to go anywhere else before then, IMO. He could go to Saudi in 3-4 years and still make huge money just like Ronaldo. Only Salah can decide how much of a decline in wages he's prepared to accept to stay with us over that period. We should not ignore what playing for Liverpool does for his 'brand' through endorsements, sponsors, brand ambassadors, and everything else. Purely speculating, but I'd wager it's like bringing in a second LFC wage, if not more, so some decrease in wages from us may not be the end of the world for him.