I'm going to butt in here and throw some things out at you: Fuel injection, hydraulic clutch, dual front discs, linked brakes front & rear.
So...a Goldwing. Sorry..I had to.
I wasn't really looking at anything bigger than a 1300...but I totally see your point. One issue would be that displacement (around here) is one of the biggest factors in the price of insurance.
It would likely be at least a $100 difference.
For example, my 1999 TW200 is $170/year. That's the bare minimum coverage to be legal to drive down the street. No fire, no theft, no collision. Adding fire and theft would bring it to around $300/yr.
My 2 Vulcan 900's were pretty close to $500 each...bare minimum plus fire and theft. No collision.
Lots of new riders go out and take their (equivalent of the MSF) course, then find out that they can't even find an insurance company that will insure a new riders, at any price.
It ain't fun.....
Pricing around here is silly too. Canada so everything's automatically 30% more expensive.
I can't find an 1800 on Marketplace, but I'd assume that it would be out of my budget. It wouldn't be if I was to sell my TW, but I'm going to keep it.
And I hadn't even seen an 1800 while browsing. Even searching FB marketplace for a VTX 1800 brings up nothing but 1300's.
We have a fairly short riding season, so it's not a real bike-dense area unless you're willing to drive 12+ hours.
But yes...totally get your points.