This could be global but as bones are sellable on Eco, I feel it's mostly applicable there. The horse spawner is the rarest spawner in the legendary crates and therefore the rarest in the game but as far as income production goes it is the worst as horses only drop leather. In fact adding bone drops doesn't make it that much better but at least it's something. Yes we can have horses on our island, but horses at /warp passive can be tamed and brought back to your island already. I should actually say horse, singular given they merge. Essentially, other than being able to say you have one as some sort of flex, the rarest spawner in the game is pretty much worthless.
I don't think we should balance skyblock around the economy of item trading. Horses don't naturally drop bones, (unobtainable) skeleton horses do.
I agree with this in general. Perhaps they need to change it out for something more worthwhile. Or have it spawn skeleton horses.
If the perception is that rarer items should make more profit then perhaps they should significantly increase the probability of getting a horse spawner from crates.
Increase probability or profitability. Increasing the probability will devalue those already in circulation which is an issue in itself given that, other than questing for a month, the only way to get them into the game is to pay actual cash. Being stung in the pocket in game is never well received. Being stung for real cash, even less so.