Some do, some don't. Modelhaus kits are going for 4 or more times what they went for when they shut down.
My vintage Revell parts-packs had appreciated hugely up until Atlantis repopped several of them.
But that doesn't bother me particularly. I bought the originals with the intention of building them, and the availability of repops just means I have more source material to build from. For instance, I can do as many Fiat altereds as I want (lots), with no worries about running out of first editions.
What with old tooling being dusted off and brought back out, and the looming possibility of accurately scanned repops of long gone tooling hitting the market, it's probably not smart to buy models as "investments".