For my first OpenHAB setup I wanted to replicate a Nest thermostat. Nest cost about $230, and I needed 2 for both my upstairs and downstairs HVAC units. Total $460. 
I figured with openHAB and by buying a Raspberry PI (CanaKit) $70 and a AeoTec 5 Gen z-wave stick $45 that I was well on my way to automating my HVAC system for less than the cost of 1 Nest. But, all of the thermostats where expensive. Until I found the Remotec ZTS-110 - Z-Wave Smart Thermostat. I bought the first one for $70, and the second one for $65.
For a total cost of $250 I was able to replicate the functionality of 2 Nest thermostats, and setup my Home Automation base platform.
