PlankBender, what you are missing is that it would not be possible to get a Garmin GNS-430, plus the GTX330 transponder, plus installation, plus the relevant drawings etc, for $15,000 – and the whole combination will not give traffic on the screen.
To get traffic on the screen you would have to purchase a TCAS unit, which would cost another $15,000 to $20,000 or so - say, $40,000 in total.