Yamaha seems to have the biggest price difference between currently available models. A psr 650 at $800, psr 750 at $1,200, a 950 @ $1,900, then a T4 at $5,200!

Ketron went from a $2,000 sd5 to a $3,900 Audya.

Korg from a $1,200 pa600 to a &2,900 pa800(900??), then to a $3,700
pa3x.

Roland a bk-3 at $650, bk-5 at $1,000, to ???

All of the associated costs mentioned are involved in every model at some point after conception.
I know we're talking lower MOTL and MOTL vs TOTL, but $1,700-$1,900 difference from two manufacturers, and a $3,300 from Yamaha, who are reasonable between their MOTL arrangers, then dispose of that logic when offering the big boy. Roland is reasonable (between their two BK models)until we see if they do a TOTL model- not likely from the chatter I read..

But as stated, it is what the market will bear when you look at TOTL. Not so much supply, but demand. Prices won't change if the demand doesn't fall and enough people are willing to pay.