Personally I don't buy stuff from Ebay, apart from one or two items that are absolutely never going to appear locally, like newly made retro items and such.
Looking around the forums' posts it's clear that in some countries Ebay makes no sense and is not a reference at all for pricing (and local sellers who base their prices on it quickly find out that people won't buy them), whereas in others Ebay can even be the only way to obtain stuff. Generally less richer countries still have retro stuff appearing regularly as people kept the stuff longer and don't discard it so easily. On the other hand countries like Germany had their citizens accessing home computing earlier than normal, and is more common place to find 286, 386 there than in other places. A user made a thread not long ago asking for help as he couldn't find retro stuff in Germany, which left me a little baffled really.
E-recycling policies are also a big factor. Switzerland used to be a heaven for curb pickups with absolutely incredible stuff, computers, truly high end turntables, speakers, amps, you name it, left on the street for people to take every single day. Lots of immigrants picked stuff up in their trucks, filled them up and transported it back to their countries to sell. Eventually they changed their laws and now it's next to impossible finding the most uninteresting of beige cases in the used marketplace, and nothing left on the curb. People there today either already collected their stuff in the past or have no other way than to buy it abroad, and with expensive importing charges from the EU or beyond. So there are no perfect realities. The United States have more stuff and variety than any other country but it's all very spread out through its huge geography, apart from California or Texas for computers, or Seattle for gaming, at least in the past...
Buying locally or inside my country allowed me to have access to what I wanted and needed and I'm quite happy at this point, I'm not a collector, just wanted to make some specific builds and that's it. ISA Sound Blaster cards are a little less expensive than on Ebay but not by much, maybe 25 to 50 euros on average, as not a lot of people had home computers around here in the 386/486 era, and those who did a lot of times had only the PC Speaker which was my case as a kid, so a SB Vibra for 5 euros ended up being more than enough for me. So the sellers in that regard try to push it slightly upwards. But you can circumvent that as complete 486 PCs usually start from 50 to around 100 euros, so you can just go for that if it makes sense to you. Moving on to Pentium era then it opens up, and you can get Pentium, Pentium II, III or IV computers for anything between 5 to 20 euros if you're patient, and if you pick it up locally most of the times you get the full peripherals set and whatever else. And it's always more rewarding than paying the same price for a specific part.
I was prepared to wait patiently for an Inwin A500 case appearing, as my father used to have one, and I wanted to build a 1.4Ghz Tualatin based PC in it to finish my builds. It popped up locally a few weeks later for 10 euros and it came with a useful Asus CUV4-X... Got some 17" Samsung SyncMaster CRTs for 5 euros each and I'm done. So of course Ebay makes no sense.
CRT TVs are easy to find and cheap too... but as people said it's different with retro consoles everywhere apparently, it's all getting very expensive. Apart from the Mega Drive and Playstation which sold much more here, it's all going upwards non-stop, especially the games themselves. If you want a ZX Spectrum it's getting up there now, and even more for Amigas... But if you want a Pentium era PC, especially a socket 370, it's still very cheap and easy to find.
People forget for example when they see the images of smashed CRT monitors and TVs in shipping that some folks truly don't have any other way of accessing these items anymore, so they take a chance...
But in general all around I feel it too, it's definitely calming down price wise. We're not getting any younger and there's already a living generation to which all of this will just be junk, either in perception or literally as it won't work and they won't have the skills or even the will to fix them up. So as I see it use your stuff, cash in in the next 5 to 15 years on your collectibles that you don't use or got as an investment for future sales, and be happy!