I remember back when I was playing maplestory, I had rare items that were only available at launch but I had paid a lot of in game currency for them years later.
I kid you not, weeks after I had obtained them, Nexon released a special crate that contained, you guessed it, those same items that were considered collector's items.
All it takes to crash the prices for these is if more topre sets are produced.
However, like I mentioned with the sansui headphones on another thread, if there are no more stock being produced then the prices will likely never recover.