Frame is simple already.
Its just pressed metal sides and a bottom tray and the tooling for that is obviously made already.

You don’t want worse faders, I’d rather still want them improved s bit, that would raise price rather than lower it.

There are several circuit boards in there. In a re-design perhaps they could miniaturise a little bit and redesign the armrest and reduce the overall size a bit.
The headphone amp in the master unit could be omitted.

Unless Yamaha is ok with lowering the price and earning less/unit I really don’t see a way to make it a lot cheaper.