Well their plans are to win the UCL. What would you choose as a player:
a) Free French league title every year in a boring league thats won by freaking December and a (growing by every year) chance to win the UCL which isn't that high
b) Playing for Barca or RM, fighting for the La Liga title vs Barca/RM, ATM and others and a good run in UCL,by being 1 of top 3 favorites. Not to mention the chance to play with MSN/Ronaldo, IniestaBusi/KroosModricIscoJames or whatever.
I know.... Look at it this way man.
On one hand the guy must be offered:
1) Ridiculously good amount,
2) Regular playing time no matter what (which he might not get at, say Barca, I mean Thiago a home-grown player thought so and left. And many young prodigies lost their impressive run of form & promising career coz of their move to Real!)
3) A plan to improve the club prospects and may be a promise to bring in a manager like Pep (I know he is going to City, but City were no better than Paris 5 years ago!) which could improve their chances in CL too!
On the other hand:
Yeah he would get to play with the likes of MSN, and of course playing at Camp Nou would probably be dream come true for any footballer
At the end of the day.... Career prospects of a footballer means earning as much as he can and, if he is a good player, leaving behind a legacy! I am sure he will be earning tons at Paris, definitely better than what he would earn any where else and if, just an
IF, he does help Paris to achieve some thing beautiful, that's it he left a legacy behind him!
Depending on how good a job they would have done convincing him that PSG does have a promising future, he might not exactly have taken a wrong step!
And then again.... Lucas Moura was also considered to have a great future, the next big thing, many cried a river when he signed for PSG and etc... But what happened? He is now available at a markdown price and still would have good chance to experience the pinnacle of a footballer's career! You know, winning Champions League!! You know it's very much possible because he still has over 10 years career left, just like Verratti!!