How much can i get out of the box figures for, they would be just for display
The line doesn't actually devalue figures used for display. It's rather rare to find "Sealed" figures on eBay or even here. They are usually jacked up in price a bit when they are, but the VAST majority of the figures you're going to see around the same prices.
I guess it depends on which line you're talking about as well. Figuarts especially don't really devalue much right now.