More people are doing a lot of things more than ever since there are a lot more people than ever. Even if the number is that high, which I doubt, it is dwarfed by the OEM market. An estimated 340-350 million PC's were sold in 2021.
Number was at least ten million PCs custom built by consumers, ~
10 years ago. I threw that out here as the bare minimum estimate. More people than ever know how to build their own boxes--and/or upgrade them piecemeal these days--and the market for peripherals sold separately is
gigantic--take a look at Amazon and Newegg. "PC Part Picker" didn't exist a few years ago, and you can buy programs available on Steam and elsewhere to show you how to build a system--which are nice resources for n00bs these days. When I was a n00b, it was 100% flying by the seat of your pants.
I'm not really sure what your point is. For instance, I haven't bought an OEM system since 1995--last system I ordered was a Micron for ~$4700. "Rolling my own" is far better...
The only point to be made is that systems built with cherry-picked components
aren't ever estimated, but judging by the incredibly huge market for peripherals sold separately (motherboards, PSUs, CPUs,GPUs etc.) it must be huge. I'm not sure why you'd want to dispute that...? I can't really see a problem with pointing out the obvious--that millions of systems are never counted in this bunch. Could be 20-30 million these days--who knows? Estimates are between 1.5 billion and 2 billion people use computer tech globally every day now...
It's not just that there are "a lot more people," it's also that a lot more of them know how to assemble a PC from components than was true 20 years ago, etc.--it's about as difficult as Lego blocks, etc.