If we can do mobile phones for $100, why can't a smart cookie develop ADSB-out for everything aviation? Sure, add another zero onto the cost, but wouldn't a decommission of maybe 3 or 4 VORs/NDBs pay for that?
i.e. is it really that hard to develop a device that does ADSB-out at low cost?
Add a cheap tablet that interfaces via bluetooth to an ADSB-in receiver (say, coupled with OzRunways or similar) and - wow- our situational awareness suddenly improved 100 fold.
Now that's safety improvement.