The club's financial situation makes it difficult for Barcelona to sign players who have a high market value and they prefer players who have a low bid value but have proven quality. Guler is also one of the long-term prospects for Real Madrid and they can invest in young players for potential for the next few seasons because Real Madrid has the stable finances to make long-term prospects, as did 16-year-old Endrick.
Barcelona need the right players in an unstable financial condition like now and they have to look for players who have a value that is not too high and vice versa with a salary. Even though Guler was rumored to have moved to Barcelona, in the end Real Madrid was much better prepared to accommodate the player.
Barcelona finances have not improved enough after the club experienced a financial crisis last season. Not strong finances have indeed become a difficult thing for Barcelona in targeting players who have high release clauses in this transfer window. I have seen that there are two players that Barcelona failed to get in the transfer window this season where the first was Brozovic who they wanted from Inter Milan but in the end Brozovic chose Al Nassr as the next team and the second was Arda Guler who joined to Real Madrid compared to Barcelona.
So basically a salary offer will also trigger players be reluctant to join them if another team is able to provide a bigger salary. But on the one hand Barcelona have got good quality players in this transfer window without having to spend money because Gundogan is a free transfer player that Barcelona got in this transfer window.