Well, it's pretty simple:
700 million euro roughly translates to $826 MILLION. That's a lot. Seems like maybe you suck It up for a year instead of having that clause go into play.
The player would still prefer to leave and join Pep Guardiola at Manchester City so he can begin a new project away from the Camp Nou. However, Josep Maria Bartomeu refuses to accept anything less than the €700m stipulated in Leo's buyout clause. He doesn't want to make a 'friendly pact' with his star man which reduces Messi's options greatly.
I can't stress how big this sort of story is. In terms of just leaving teams in general, this is the world's version of LeBron joining the Heat. But now imagine if Dan Gilbert, instead of writing in cosmic sans, decided to take him to court and refuse to let him leave. Actually that'd be awesome. That's content. Gilbert should have tried doing that.
And what happens if he returns for the year? That's gotta be the most awkward year in sports. He's just gonna go play with teammates who know he wants to leave and a front office that knows he's leaving. Now that I think about it more, I hope Messi goes full Costanza. Just refuse to do work. Be as lazy as possible.
So now I guess Messi is going back to Barcelona for a year and then Manchester City? Who the fuck knows. $826 million is so much money.