You have to mail the cube to whoever buys it (which includes paying for shipping, unless you want them to pay for that as well).
If you have a used cube, you're generally going to have to sell it for less than what you bought it for. I doubt you'd sell that cube for any more than $5 or so, seeing as you can get it here for $6.15 (and you're not an established cube seller like cubezz or other cube stores, so people are taking the risk of possibly not getting the cube).
lol this thread is silly. I would suggest $5-6 USD, maybe even less. This cube is not particularly in demand right now, as there are cheaper and better cubes.