This is one of the reasons I hate that we've started to use this tactic. If Lavia is already valued at £50million by some clubs then next summer he could be £70-80million. City sign him for £40million and immediately flip him for double that, screwing us out of £40million.
This technique is fine and dandy in theory but it's going to make us fans miserable in the long run mark my words, we'll get good players for one season it'll be like having a new team of loaned mercenaries every year.