Once you buy an item, it is yours to keep, sell, or trade. At any price you want. If you buy from a member here and sell it for 3x more on eBay, that's not shady.. that's business.
The only problems I have are when people lie about the item, recast the item, or take credit for the item.
As for this thinking that if you buy something from a member here you MUST sell it for an equal or less amount of what you paid..it's just stupid. That's not how the real world and market works.
I buy raw kits all the time, and sell them at increased prices.. (you know, on account of the paint work?) and some members were questioning me about THAT. People need to just mind their own business I think..