Something I have always believed, and probably always will, even if I am proved wrong, is things made to be Collectable, do not over time maintain inflated prices.
Working in the coin industry, we sold mainly rare currency, but also modern "collectors" coins. Some of them would go up a lot for a while, but a few years down the track you couldn't give them away, I have many times gone to the reserve bank and cashed in for example Olympic bronze $5 coins, which we couldn't get enough of in 2000 while the games were on and shortly after.
This may or may not happen with mondos.