There have been a number of CFIT accidents in GA over the past few years.
The ATSB reports have generally recommended the fitting of GPWS/EGPWS equipment to the aircraft, but CASA have not taken action because the costs have been considered too high for minimal gain.
TAWS B is significantly cheaper than TAWS A. If the NPRM goes ahead, then the most common TAWS B solution will most likely be a Garmin 530W, which not only meets the TAWS B requirements, but adds a new VHF Comm, a new VOR and a TSO'd C146a GPS.
Is $23,000 a lot of money? Yes.
Is it that much extra compared to the maintenance on an old Comm/VOR? Not really.
Did it just save my business money if I managed to get in to an airfield with an RNAV approach with lower minimums compared to the NDB approach? Absolutely! (And my customers are happier!)
Will spending $23,000 bring my mate back from a CFIT accident a few years ago? No, but it might stop me losing another friend - in which case it's the cheapest $23,000 I ever spent.