Sunny,
A bit more about US pricing, make certain the units you are looking at are 1090ES ADS-B prices. Adverts. even from manufacturer's web sites, don't always make it clear.
Remember in US you have two choices, 1090ES ADS-B, a rewarmed version of fifty or so years old technology, (actually closer to 1938), the 4090 channel transponder, and the UAT system, a CDMA broadband current technology datalink that carries far more than just ADS-B.
It is the modern technology UAT system that is dirt cheap, compared to what we are stuck with.
Tootle pip!!