I do often think about how much of the instrument needs to be handed.
Taking the Fender classics Jazz & Precision...
The neck is a separate part, it does not need to be handed!
If the side dots were printed on both sides, I for one wouldn't mind if the tuners were on the top or bottom edge (looks kind of cool "to the floor" and some righties guitars have been designed that way). I'm not aware of any tonal problems with strings going on the reverse order of tuners. The nut is reversible as it is.
I'm aware of one supplier of replacement necks who don't offer left handed - they don't need to. They are paddle headstocks (for you to shape) and they have the dots on both edges. Not suggest that left handed guitars should be supplied unfinished, just that necks don't have to be made fixed for a particular handedness.
http://edenguitars.com/bass-necks/That said, I have as many left handed guitars & basses as I do righties that I hang upside down. I can't say the absence of side dots on the latter stop me playing any, but they are nice to have.
Only the body/scratch plates need to be handed. Scratch pates are something that I for one don't want and they don't have to be fitted.
The bridge already works the same either way,
Reverse action anti-log controls on left handed guitars is an unnecessary expense. I don't want them at all. Clockwise=more is surely something even the most left-handed can handle? Wiring normal log controls to work backwards for left handers is too stupid for words.
Control plates might need to be handed, although if the Telecaster type was adopted it's unnecessary. If handed, both sides could be finished to simply flip either way. For my taste, control pates are not needed if the control routing is from the back. If shaped thoughtfully, the same cover plate can be used on either side.
Even if I build thru neck basses, only the body wings need to be made different.
If manufacturers think left handed production is too expensive, maybe they need to think about how they make the right handers first with a view to making it easier to produce left handed versions?