This made me curious, so I just took a look on eBay.
My 4070 Ti that I bought (new, oops) this past December has appreciated 20 - 25%! At least according to what people have them listed for... no idea if anyone is actually buying them at those prices.
Of course even if I managed to sell it, everything else has gone up in that time, so it's not like I'd get to make money on the deal. Pretty wild, nonetheless!