That's the customer advantage of platform longevity - older CPU see price drops because they compete with the newer ones on the same platform. Just look what you still have to pay for an i7-7700(k) in contrast.
The market - supplies and enthusiasts - are hot on the trail of Xeon and dual Xeon systems as a result of millions of CPU's being retired and resold on Ebay and other marketplaces. As you mention, Xeon's aren't the only desirable CPU's, top of the line I-7's are doing well with premium motherboards hitting new lows ~$100. With that in hand along with modern components, a very nice economically friendly pc can be assembled.
And there are all the new chips begging for attention.
In this case, it's also GloFo produced Ryzen vs. TSMC produced models, I.e. AMD can crank out 12nm Ryzen without seeing any impacts on capacity for newer ones.
TSMC is going to keep as full a booking as possible, at some point the world could hit CPU saturation...again. Basically if 10MM excess CPU's are produced someone is going to have a tough time.
A sudden shift happens at the CEO-company: "how do we sell this stuff" takes place of "how do we make this stuff".
I think it would be smart to keep those as budget options going forward.
Intel is going to have to get their prices in line, they were waiting for the moment, maybe it's here. It doesn't look like laptops are going to be their saving grace.