Expensive Trophy! Really!! Personally, I don't see the advantage, unless you have mp to waste and just do it for the fun of it. Or you really are wanting the trophy. It really has no real benefit. To me anyway. I could see it if the prize were in millions in lieu of thousands. Maybe. But within seconds the item is bought out everywhere and to win, it will cost you millions to win 200K and an egg, or, 100K The item becomes unbuyable almost immediately and unless you have hoarded that particular item, chances of winning are slim to none.
If, the prizes might be the retired, gourmet items nobody can buy ... I can see it. I don't know, it is just not my thing to waste MP on a futile challenge.