The Catalan giants are believed to be preparing a fourth bid in the region of £138m for the Brazilian playmaker's signature.
Liverpool have held firm so far by reportedly rejecting bids of £72m and £80m, and publicly they have insisted numerous times that Coutinho will not be sold before the transfer window shuts in eight days' time.
Souness believes that the 25-year-old does not warrant a staggering price tag because he is not a "game-changer".
"Players normally get their way at the end of the day and with the sort of cash that is being offered now, I'd be snapping their hand off," the Scotsman told talkSPORT.
"That kind of money you can't say no to. Is he that good? For that sort of money you want a player that is a game-changer, the difference in big games, and I don't see him as that.
"Yeah, he is an attractive little footballer, he is neat and tidy on the ball, he wrong-foots people, he scores some wonder goals, but at that sort of level I would take the money. I don't see him being a [Luis] Suarez or a Neymar."
Coutinho, who has missed all three of Liverpool's games so far this season due to a back injury, handed in a transfer request earlier this month.