Larry, you know we love you. But there's that same critical flawed statement you always make. Just because there's a market for that particular part, doesn't mean there's a product for the finished product. You have two main markets for computers. The unwashed masses that just want an appliance they can use to surf the net, check email, and maybe collect cat pictures. Then you have the enthusiasts who like building themselves a performance machine.
You are building appliances. There's nothing wrong with appliance PC's. However, if you were in the market for an appliance which sounds better to you:
An appliance from XavierMace on Craigslist (or word of mouth, or whatever) or a new appliance from a store for the same price?
You can get this from Newegg right now for $400: Acer TC-780-NESelecti5, Intel Core i5 7400 (3.00 GHz), 8 GB DDR4, 256 GB SSD Intel HD Graphics 630, Windows 10 Home. Plus a return policy from a major retailer and a warranty. There's multiple 2200G based complete systems on Newegg right now for under $500. What price were you shooting for on your build? You already said you're at $400 in parts already which wouldn't seem to include case, Windows license, etc.
Well, if there isn't a market for the "finished product" containing an APU, then why are the APU selling? Big demand for avant-gaurde keychains at the fair?
And, if anyone has half a clue, they would PREFER a Ryzen APU rig, to an Intel i5-7400 rig. At the very least, one can game, one virtually cannot. For an additional $100 on the price, many would choose the Ryzen, if they knew that.
I guess I don't quite share your pessimistic view regarding custom-built PCs. I bought a pre-built gaming rig last Dec. from Walmart. i5-7400, 2x4GB DDR4, 1TB HDD, Win10, GTX 1060 3GB. All for $500 + tax OTD. Not a bad deal, I couldn't have built one (including Windows 10) for that price. Now the new ones are going for $700+ on ebay.
But Lord help you if you want to upgrade. Thankfully, the chassis and mobo, have room for an additional drive, but other than that, you're basically screwed if you want to expand or upgrade the PC in any way.
Some people, that have had pre-builts in the past realize this. Most people don't. And you emphasizing the cost proposition to new owners, and neglecting the fact that you basically have to discard the whole PC if you want to upgrade much of it, rather than with a custom PC (especially with AM4) upgrading what you like, is a bit disingenious.
Edit: And that's kind of my point, with a Ryzen APU inside a custom-built PC, it's a lot more than just an "appliance" to surf the web, it's a "gaming PC" (for suitably lower-res forms of gaming), as well as a "media PC", a "4K HTPC", etc.