I have had two kinds of 434Mhz systems. The first was reliable and easy and it also was more expensive. Receiver was about 50£$€. Transmitter costed like a few euros. It was from UK manufacturer and I did not buy it from Ebay. All I needed was a serial bus. And the range was a few hundred meters.
The second was cheap from somewhere Ebay. It was hard to get it working and even the range was about 10meters.