#1 They would likely incur a financial loss if they sell him

When Barcelona shelled out the sum of €140m to sign Philippe Coutinho from Liverpool, they believed they were making a long-term investment for Andres Iniesta's successor, with it expected that the Rio de Janeiro native would hold it down in midfield for at least the next five years.
As it happened, those expectations have not been met (at least not yet), and the Barcelona board are said to have lost patience with Coutinho and are willing to listen to offers for him with PSG and Manchester United said to be interested.
Reports suggest that the club has set an €80m valuation of the player, and if sanctioned, it would represent bad business on the part of Barcelona.
Selling him for that amount would represent a €60m loss on a player still very much in his prime just 18 months after expending a club record fee to sign him and this surely makes for bad business.