People said it back then when warning other people about buying at inflated prices. The one and biggest factor in secondary value is the presence (or not) of alternatives of the same character, paired with rarity, character's desiderability and final quality.
You can't expect a Wolverine to be worth 2k with N-th other alternatives on the market with very few exceptions like customs made in 50-100 pieces. Or Hawkeye to be worth 1k+ when nobody really cares for the character enough and the PF is still going for 350$.
Also, the increasing number of resellers actually helped the buyers since to a higher offer correspond lower prices, flippers are fighting each other lowering their prices. Some characters will probably start gaining back value once flippers have unloaded theirs, i.e. characters like Phoenix and Thanos.
Hard to tell right now since companies are starting churning out more and more characters and interests shift quickly.