Once the CAD and CAM work is done, there'd be no time or cost difference to manufacture a left handed chassis vs a right handed chassis. It likely uses the same fixturing, even, I would guess. And, they already had both, apparently. They had to incur costs in programming to make an ambi chassis. What it does is cuts the number of SKUs in half, and allows them to stock and manufacture a single part.
I'm not the smartest guy on the planet, but I fail to see how eliminating one cut and adding another, with same number of setups in manufacturing - and a side effect of decreasing logistics load (by going to a single SKU vs. two) would raise prices at all, much less "without raising them too much"? They should be decreasing their costs overall, not increasing them at all. The only thing it speeds up realistically is delivery of left handed chassis? The vast majority of the time of manufacture for a chassis of either handedness is still there, either way.
My friend had to wait 7 months for this chassis, as is, and it's ambi (not left handed specific)... So apparently, it's not speeding anything up at the moment.