Dropped $180 on a coaxial indicator after a crash in Fort Worth, and it paid for itself on the very next setup
If you run a lot of one-off parts on a mill with no probe, a coax indicator tells you true spindle center in like 30 seconds instead of sweeping an indicator and doing trig, and after I nicked a vise jaw on an off-center bore it was the cheapest insurance I've ever bought, so what dumb little tool actually earned its keep in your box?