Happy for the Frankfurt fans who already paid 500β¬ for a ticket that will be invalid for them. As to the socios, there should definitely be a punishment to sell their tickets in this game. The reselling system has it flaws, but it also encourages people to become socios in the first place, which is why the club keeps it. The system is intended for the honest fans who really only resell, if they can't go, not to make money. That ensures always a full stadium and the club earns even a bit more money. The problem is always, when people start to exploit these systems for their own benefit.
The easy thing to fix would be to up the mandatory attendence in order to keep the seasonal ticket. Make it like 75-80% of the games per season and only make exceptions for medical reasons.
And since the resell is only allowed on the official Barca platform, set a certain maximum price, so they don't get a big plus reselling their tickets. Take away their motivation to make money with it and then you get rid of the people who only keep their season ticket for profit.