I haven't (yet) so i'm very cautious :'D
To buy items i've missed over the year when they are for sale in the market and also to buy a bunch of commons~ i want a lot of commons to work with and the fp adds up quite quickly D:
and lastly, i want to be able to afford the next (or one of the next) unique knuffel auctions
I could sell the items seperately though, last night i listed the toghu hair in the market for 50k, not expecting anyone would buy it, but it got sold! so i was really happy with that