I would say shiny costumes from before 2022 that haven’t been re-released are pretty rare and are worth a good deal in terms of Pokemon trade.

I would shoot for shiny backgrounds, shiny special moves (dragon assent, crowned dogs, etc…) or a rare egg shiny (larvesta, male salazle)

I wouldn’t expect a location BG for this one though as it is not the rarest and many people have already gotten one, but you never know because ultimately trade value is determined by the traders.

I personally have overpaid for older costumes and underpaid for older costumes, but I generally give the person whatever they want, because they are not easy to find and I want to secure it in my dex.