Hi Diki
Hadn’t checked prices, but if what you say is correct, then that is unbelievably cheap for an organ of that spec, there is certainly no other organ manufacture in world that gives you that spec for so little money. (If your into organs its definitely one to put on the list)
Apart from an actual organ I don’t know of any keyboards that fit together close, and if they were made then the price would still be high due to the low volume of production. (The re- tooling required to make the new cases would be very expensive)
BTW in the 80s and 90s in the UK, some artists took there keyboards apart and built there own custom versions to suit, (In the UK if something isn’t available we have a habit of modifying or building our own) so you could always try the same yourself, and who knows it might even catch on.
Enjoy whatever you play

Bill