Dick.
Your comments in regard to new aircraft owners is correct. If they were purchasing a new aircraft, it would be unwise to not request Baro VNAV capable avionics. Especially if it came at no extra cost.
From the existing owners perspective, where operators have already installed TSO-C146 equipment, having SBAS in this country for aviation is a no brainer. Withstanding your comments about the $150m for the country to achieve this mandate. Why don't you wait until the costs are made public so you can make comment?
As stated from previous posts, aviation will not be the only industry to benefit.
The Regional Carrier I work for has looked at Baro VNAV in the past (currently operating Legacy 1990's type Honeywell FMS). To equip for Baro VNAV is for more costly than equipping for SBAS (WAAS) LPV approaches if that service were to become available.
There are many operators who would benefit from SBAS. Perhaps a more positive outlook for it, whilst the trial is in progress would achieve a more useful discussion than just stating on Prune that there is $150m price tag attached?