As evidenced by the growing numbers of lefty instruments, the demand is there, and is being accommodated. Inevitably, instruments at all price points will be produced in lefty, whether it's by the current makers, or others who will recognize the opportunity and capitalize on it.
This is not to say it isn't being done now:
http://cgi.ebay.com/Benavente-SCB-6-String-Left-Handed-Bass-Custom-Made_W0QQitemZ250124719909QQihZ015QQcategoryZ4713QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
http://www.adirondackguitar.com/zon/lh_sonos.htm
http://www.adirondackguitar.com/lefty/warwick/thumb_bolt_on_5.htm
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Those makers who get on board will benefit, those who don't will not. If some makers considers it too expensive an undertaking, that is their choice. Others will emerge to supply the market.
BTW, whatever the point is you've been trying to make about the tooling of left-handed parts being too expensive, I'm not buying it. As you've mentioned in a previous post,
>parts< can be
>mirrored< in the CAD phase, and a cutter path or whatever other
>process< you need to make it developed from that. The CNC machine will make whatever it's programmed to make, there's no difference if it's left or right handed. Same with molds. As long as I've been working with OEMs and suppliers, I haven't yet run into a prohibitive cost for a left hand vs. a right hand part.