Yeah, maybe. I understand the reasoning of deterrence. But I'm not sure, it feels unfair.
First of all, I wouldn't say the gesture would be for nothing, it would be a strong sign of support to and solidarity with your travelling fans in any case. Then, the fact you're subsidizing your fans' tickets is because you deem Sevilla's ticket prices unfair and excessive towards guests. Well, now your ticket prices are unfair und excessive towards guests.
As I said, I understand the logic but in the end, you're taking it out on traveling fans. You're doing the same as Sevilla.