Could they sell a high-end amp without the fancy

One could argue the majority of high-end audio components embody what you ask for.

Just off the top of my head AtmaSphere, Air Tight, B&K, Bryston, Cary, Creek, Conrad Johnson, Jolida, Music Hall, Music Reference, NAD, Naim, Quad, Quicksilver, Rega, Rogue, and Shindo strike me as getting the chassis done while exercising fiscal prudence.

Personally, I think the AtmaSphere Novacrons rank among the most beautiful audio components ever produced, and yet Ralph's chassis get done at quite modest cost.

Please also take note of Decware Torii Mono amps at Decware.com. I have no affiliation except happy customer.

Always considered the industry to be very conservative. Would like to see more creative bling and design, other than blue lights. Halcro was unique.

You do need a minum quality casing, or the sound will be impaired. Take Conrad Johnson for example. I used a premier 17 Pre for a few years and very good it was too. However the thin, resonant top plate did'nt do it any favours at all and needed some weight on it, to improve the sound.

I do take the point though, cases milled from solid obsidian with diamond inlay, would be overkill.

The names you mentioned in the OP are higher end brands . Would you want a high end car with an exterior that only Mr Bean could love ?

To be honest I've done my share of weighting the tops and adding insulating liners to the interior's etc etc to components to dampen there flimsy containers , but I'd just as soon have structural integrity up front and pay for it .