~snip
Isak has done a lot for the team and no doubt they club needs him to stay but if he decides to move away then is still good, this is not the first time Liverpool has shown interest but now he is ready to move so why hold him?
Take the cash and go get a replacement, Chelsea has face similar situation when Eden Hazard left to Real Madrid but although this is more difficult selling their star man to a rival team in the league, sorry but they just can't hold a player against his wish.
In the case of Newcastle, I guess they placed themselves in that situation. Seeing that clubs where getting interested in season sometime last season, they decided to place a fee of £120M just to scare clubs away. That alone is enough message that they are willing to sell the player but for a higher amount. Liverpool have now proven that the money is not a big deal, leaving Newcastle confused and in a hot seat at the same time.
Players are some point will definitely leave the club. If a player feels that the system doesn't suit him/her, then they should be allowed to leave. Like someone said, clubs also do the same to these players.