I think that MAYBE the difference in price between TOTL arrangers and WS's is simply a matter of economy of scale...
There are probably a hundred WS's sold for every arranger. Of course you can charge less if you are selling those kind of numbers
But sadly, the truth is apparent if you look at the keyboards without any preconceived notions. You can buy an 88 note, TOTL ivory feel piano action WS for the same price as a 61 arranger with a plastic body, cheap knobs and buttons, much smaller display, and next to no I/O options.
And, unfortunately, you can't even look to the styles themselves as a cost difference, nowadays. All the TOTL WS have HUGE libraries of very complex 'arpeggios' or 'loops' that are just as hard to program as a good style. Add to that chord following abilities, and it's getting harder and harder to tell them apart.
Except, of course, when you have to pay for them.
A TOTL 61 WS like the MotifXS is close to $2199. It's equivalent arranger cousin, the Tyros3 is going to be about $3500. Same keybed, similar display. A LOT of sounds in common. SA voices, Mega voices, Sweet and Live, etc..
Other than the underlying OS, what, on a T2/3 could POSSIBLY be worth an additional $1300+? It certainly isn't the build quality, and no-one in their right mind thinks the Yamaha harmonizer is worth $200, let alone $1300!
So you tell me... do YOU think it is economy of scale, or are we just being ripped off like the wealthy retirees we seem to predominantly be? Because no WS user out there is EVER going to be willing to pay $3500+ for a cheaply built 61 note WS, that's for sure...