Originally Posted by
tistisnot
But ADS-B is no good low level countrywide for ad hoc helicopter operations
Is that really your personal experience of ADSB-out?
Mine (albeit in a simple bushplane) is quite the opposite: i.e. that extended squitter with SIL 10^-7 ensures scarily accurate FR24 tracking in upland Britain well below the height at which en-route compliance with the common rules of the air would not be assured.
As for the cost of ES, it should be around 1 AMU unless the rest of the stuff in the panel is 15 year old junk.