It is apparently being exhibited to draw attention to the ludicrousness of extreme wealth. If that is indicated at the exhibition, it is making a valid point, so it is being useful.
Making something out of gold that has been bought legitimately isn't an abomination. (it probably isn't solid gold anyway - that would be very dificult to manufacture) If it is solid, then as someone else has said, it will probably be melted down eventually and made into hundreds of smaller objects - jewellery perhaps, which would be sold and the profits would go to . . what? Would the money be spent on the poor? I doubt it.