I've seen rugby and soccer balls in overheads. I think it's best to deflate the ball a bit, in line with the advice on transporting bikes, but that's probably an excess of caution. The cabin is pressurised to the same elevation as México City, and I think they play football there. Strictly speaking it is part of your baggage allowance, I suspect you'd get away with it, but deflated there would be no issue at all, I guess. (And yes, that much for a football? I doubt it cost more than a fiver to manufacture).