I don't think it just about wages, or he would have been with PSG. They trashed him publicly.
He will get the 10mil a season from someone, I'd rather be Barca getting him on a free and with him motivated to prove France and PSG as fools.
The major reason Barca pays high wages because they have the most valuable and talented squad in the world. Run your club like Spurs and you can be outstanding if you keep making the screwed moves but never great. In today's world you better spend (fees and wages) like Barca, PSG, Manchester clubs, Real, Bayern. Big wages don't assure you of performance (United, Arsenal, Chelsea) but without it you are not going to be Europe elite. BTW Liverpool and Juve are just out of this group but top 10.