Figure a million dollars a lane at that point — on top of a ~10m initial investment.
On top of air handler issues, the confined space increases risks of TBI/CSE. Even suppressed carbine/rifle fire isn’t hearing safe / and so to make safe working conditions one end up with a much larger range.
So your 10 lane range is now widened to what 30-50 would have on an outdoor. And now you are at a $50-60M range just so you can cycle 10 shooters at a time through a PWT?
Outdoor ranges are vastly preferable.