I think it's a little unfair to say it was mainly financial reasons that he went to Barca. As I understand it, Coutinho actually paid part of the transfer fee himself to make the move from Liverpool to Barca (£7 million has been reported) and his wages at Barca weren't considerably higher than the £150k per week contract he had at Liverpool.
He left a Liverpool team that had finished 4th the season before, 17 points off the champions and had finished 8th the season before that! He won La Liga in the first 2 seasons he was at Barca, he won the Bundesliga and Champions League with Bayern, he won nothing at Liverpool.