Ah, now I understand. I thought you were referring to broadcasting revenues as a whole being 5%, not the share they were selling. Still €40m over 25 years is €1bn of revenue you'd be selling off for €500m. Seems a bit drastic.
Well it'll be a bit lower than €40m, since the total broadcasting income of €165m consists of national + international rights and as I understood it, barca selling only the national rights. Also it's not even clear how much percentage the board will sell. They are allowed up to 25%, but what they'll do is another matter.
But still it's of course a bad decision to give away 25 years of income for half it's value. Laporta made it clear. There is only one other choice and it's even worse: to do nothing. With nothing, you get nothing and barca will drop out of the big clubs round. That means less fans, less money, no means to pay debs, lights out.
Thanks to Bartomeu, barca is forced to do this deal to stay relevant and competitive in the next years. And as I said, 5% is no small amount to give away, but far from crippling. Especially, if sales increase, the 5% will become even less.
Barca wants also to find a strategic partner with a big network to increase sales in merchandising and tv. If they find someone with a good knowledge and network, both will profit. There is still a lot of room left to improve on that front, since PL getting double the tv money than LaLiga, while LaLiga won the most international trophies in the last 10 years.
What they aren't willing to accept is to swallow the bitter medicine/pill now by insisting on fixing the problems on one hand and then insisting on buying or bringing in more players on the other.
You still can fix current problems without stopping transfers. The problem is not the number of players, but Bartomeus contracts. Laporta and his board already set a new wage system which will reduce all wages to a healthy €400m, when Barto's contracts run out. Every player who signs a new contract with Laporta's board is within the new limit. Look at Araujo for example. He accepted the new limit at barca. United offered him nearly double and Laporta didn't match the offer like Barto would have done. Take it or leave it and Araujo took it thankfully. That's also a big reason they want to sell FdJ, because he exceeds the limit by far with his 19m gross.