I throw out my boxes because I have no space to store them. Like what RED2 said : As a seller I make sure to account for box or no box in my price. As a buyer I don't care about the box actually. To save on both the figure and the shipping.
Some boxes provide better storage of pieces/parts than a baggie or some other form of storage, so I do keep some of them (i.e., Official MP boxes for instance). Otherwise, typically boxes go in the trash. As others have astutely noted, boxes take up space and space is better allocated to display.
That's better than her selling them at some random prices, like all cars and Dinosaurs $20 each, in a yard sale.
If you are on the fence about keeping boxes, just think for a minute about if you would buy empty boxes.
She's 12 years younger than me so honestly, it's probably most likely going to play out that way. She's pretty up on what I have that's worth a lot and what isn't. The scary part is when you find out she has this mental spreadsheet of what your stuff is worth....for when you die...and I'm not even sick yet.
I throw away the boxes. If I bought second-hand, I would not care about the box, and most certainly would not pay more to get it; I would instead look elsewhere.
I used to kept all the boxes for storing the toys, but now I just throw all the boxes away and used seal bag to store the toys. Trust me it will safe more space.
Pretty much guaranteed you’ll be losing money on resale for higher end 3P figures - e.g. Fans Toys - without the box.
My wife is 12 years my junior as well. Hooray for cradle robbing! I never really thought about her selling off my stuff when I die. Just figured it'd go to my nephew who likes Transformers but I suppose she could do with the money. Hopefully that's still a good way off, though. I keep boxes because of some weird tick in my brain or something. I have no intention of reselling any of my figures but without the boxes they just feel less valuable. Besides, it's nice to have them to repack the figures when you move.
You're likely to get more on a sale with a box...likely, but not guaranteed. But how much is that space worth to you? Is keeping a box for a year or two or eight worth a few extra bucks? Me, I keep the boxes to the more collector oriented figures of my collection and throw out the retail figure boxes.
I always keep the boxes even if I never have an intention of selling the figure because, well things can always change. Never thought I'd be selling my Binaltech/Alternators but it looks like it's gonna happen and I'm glad I kept the boxes.
I think I've chucked every 3P box, even stuff with artwork/packaging I really liked. I just don't have the room to hang onto boxes under "just in case" scenarios. The few boxes I do keep take up enough room already.
I think it's possible but the challenge here is the styrofoam. Corrugate inserts can be used to house simpler shapes like a computer monitor in conjunction with an EPE bag to prevent scratches. But, I would not want corrugate inserts only to protect a 200+ figure since there are more fragile small parts. I keep all my boxes cuz OCD. But also I think it completes the set. I have not really run into space issues yet so I'll probably have a different response in about 2 years or so. =P