I did read that the prices range from USD2K for the most basic VFR output system, up to around 20K for the 'all singin' all dancin' equipment, plus installation etc....
The other side of the coin is the cheapest units in the USA are the 978 MHz UAT systems for GA use below 18,000ft like the Freeflight Ranger systems
Although apparently 2 thirds of installations in the USA are 1090MHz.
All-in-one panel mount 1090 is only the new Garmin and L3 Lynx - apparently L3 are revising their pricing for 2016.
But again, we are 3 years early and there are still units coming to market.