I don't think the prices will go down at all from now on, if anything they may creep back up. Supply vs. demand. The last couple of years, the demand was not there, the prices were a bit high and the looming deadline was still far off.
I'm not so sure. Just because demand will go up doesn't mean that supply (and new market entrants / competition) won't go up even more. There is no inherent scarcity in ADS-B transmitters like there is in some commodities like oil - ramping up production is certainly not hard, and as more companies have time to meet the TSO and add competitors to the market, I doubt prices will rise. Especially in the EAB arena where we may have the option to install units that meet the standard without being certified.
Demand for large screen TV's has skyrocketed over the last 5 years, and yet prices have plummeted. (Actually demand went up because prices fell, but goes to show that both can happen together).
Where I CAN see increased prices is in the installation shops as the deadline approaches. There IS a limited amount of labor supply. Good thing I can do my own
Now, I could certainly be wrong (I have a scrap heap of parts that proves it's happened before), and if I were building my panel today, I'd probably save myself later trouble and install ADSB-OUT now. But for right now, I have the benefits of ADS-B weather, and some traffic.
There may be an infinitesimal chance that I collide with a plane in mid-air that I would have been notified of with full ADSB-Out, but even being notified of a target doesn't mean you won't hit it. The current price tag of reducing this risk just doesn't do it for me. Not when I could do a year's worth of flying, or install an autopilot, for the same cost.
Chris
PS - I agree that even if not the stated intention, having every airplane in the sky identified will be way too sweet of a revenue stream for the tax man to pass up. It's only a matter of time. There won't be much sympathy for us "rich" airplane owners.