Why some games like Tombi! (aka Tomba!) or Klonoa from PSX era are so expensive?

I check on ebay, and their prices r ridiculously expensive basically

Especially Tombi... it'd b a miracle if u find it under 100 bucks... even the disc ONLY, without cases, and manuals!!

I don't get it... it's not like a Colector's edition or sth, just a plain PSX game... i know it's rare and all in our days basically... but who would buy it at such a high price?
Why some games like Tombi! (aka Tomba!) or Klonoa from PSX era are so expensive?
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