Hi, Theophile!
I’ve written a lot of stuff over the last thirty years, both in print and many different Internet forums (going back to "rec.audio.high-end" in the days of the Arpanet). That’s when I was still at Tektronix in Beaverton, Oregon, and had access to lots of test equipment.
One thing to note is the first capacitor in a classical CR or CLC supply is not actually a filter, and making this cap too large can create very large current pulses in the power supply, which then radiate out through the power cord and into adjacent equipment. Big transistor amps with more than 40,000 uF in the power supply are the worst offenders here. A bridge rectifier can "snubbed" to smooth out the worst of the current pulses, but the snubbing circuits must be tuned for the exact brand of power transformer. A mistuned snubber will actually make the ringing worse, so it’s not a one-size-all solution.
As for pricing, Spatial is clearing a profit, but it’s not particularly large. Vacuum tube equipment is expensive to make compared to solid-state. Audio transformers are labor-intensive and the steels in the core are quite specialized and only made in small production runs. Vacuum tubes are not made by robots, but by experienced labor, in small production lots. Spatial uses hand-soldered point-to-point circuitry with exotic wire, instead of circuit boards, and switched-resistor volume controls are several times the price of conventional rotary controls. They are not made on a production line; one tech sits down and builds the whole thing, another checks his work, it goes on a burn-in rack, and gets thoroughly re-checked before final approval.
By contrast, the most expensive part in solid-state gear is often the custom-machined front panel and case, followed by the power transformer. Transistors range from a few cents to a few dollars, and op-amps are rarely more than ten dollars each. Circuit boards are not that expensive if you buy them in lots of a hundred or more. So the actual working circuitry is surprisingly cheap, often less than 5% to 10% of the retail price.