It's a retired costume trunk, originally selling for 500 CSC. I price checked the individual pieces, and you can buy the entire male set or the entire female set for about 20m sP, so obviously I won't go below that.

I'm trying to sell the unopened trunk though, and there aren't any others available in trades or shops, so I imagine it might be worth at least a little more. Any ideas?

[edit]

Sold for 600 CSC and 7.5m sP