I think the selling point has already gone. For me it was the summer of 2018, Madrid or Barca would have looked at any of their front three and gone ‘just coming into their prime, not yet on mega wages, best days ahead’ and had the cash to buy them. Plus they wouldn’t have had to do a hard sell, Madrid and Barca were far more appealing at the time.
Now though these players are 28/29. Madrid and Barca just don’t buy players at this point for mega fees and for good reason because their best years are either limited or already behind them. The oldest was probably Suarez at 27 who was smack in his prime and didn’t really ever have much pace anyway. He was also miles better than any of their three now.
There’s just no way a business case stacks up for these players. A pace player, who works well in a high pressing system (which neither of them play), has too many miles in the tank already (e.g Firmino is no longer good enough for either of them) so might decline very quickly after 30, demands a huge fee in the market (which neither can afford), will have no resale value, only Salah has any commercial value, they will demand a huge wage because they’re already on that at Liverpool and none of them are better than some of the players already in place (Hazard).
Compare that with targets like Haaland , Sancho, Mbappe. All have their primes ahead of them, all would probably cost the same. The Dortmund lads might even be on lower wages. All have huge commercial value as the next stars of the game. They’ll hold any resale value for longer if they become unwanted at some point.
If you’re an exec in the boardrooms of Madrid or Barcelona it’s not even a question. A star for the now and future or for the same price a player on the decline? Top clubs don’t buy those types of players.
My view is that Salah will agitate for a move, and not get it, but will use it to get a better deal at Liverpool, which Klopp will give him to keep his team happy. Firmino knows he’s not moving upwards anywhere now so will angle for a longer deal and Mane probably will do the same. Klopp will then go off into the sunset as soon as he stops winning and leave that front three, Thiago, Henderson, Van Dijk, all on eye watering contracts and all in decline for the next manager to sort out.