Well, on CPUs I can agree with you but that's true for most CPUs. You can easily buy 486s, Pentiums, K6s, Pentium IIs, IIIs, Durons, Athlons, etc...
Usually only the top of the line chips of a certain generation (K6-III+) or with strange quirks (looking at you, FDIV bug) will be quite expensive.
But mainboards, well, that's a totally different story and I think we're already seeing how LGA 775 mainboards are becoming less and less available.
Don't get me wrong, that alone certainly would not justify a price increase because a shrinking supply means nothing if demand still doesn't outmatch it
but all in all I think we will see a price increase.
I mean one needs to stay realistic, even very good super socket 7 boards can - with some patience - be bought for roughly 40-70 Euros and today I bought a
socket 3 motherboard with PCI, Aladin chipset, CR2032 battery (no Varta, yeah!) and onboard IDE and FDD for ~50 Euros.
And they will very likely stay way more expensive than LGA775 boards but I do think that in the future people who grew up with them do want to have that
"feeling" again. Don't get me wrong, I'm not talking about "investing" in hardware or anything, just that I'm expecting an increase in demand.
All in all this is just a hobby in my eyes and yes, some people see this as investment and maybe some make their livings from it but I can much easier just invest
in stocks and funds so to me it is all about the hoarding, ahem "collecting". I never sold anything until now and it is very likely that it will stay this way.
There's also one other caveat: prices in this hobby can also decrease. I remember that I had to pay more one year ago for a not nearly as good 486 mainboard
and more for 2 super socket 7 boards. I was successful within the last weeks in acquiring much better boards (486 and Socket 7) for much less.
I also got 2 Socket 370 boards for next to nothing.
So this is also often just about trends. I remember when Phil did some videos and nearly immediately prices increased on hardware he used. Later on they decreased again.
I even know a listing on a well known auction site where the seller specifically mentions Phil and links to one of his YouTube videos.