What's the cheapest solution for thermostat and are they worth it?

[RBoy (www.rboyapps.com - Making SmartThings Easy!)]

If you don’t have a c wire you can use this Venstar device to create a c wire from your existing wiring.

[RELEASE] Enhanced Z-Wave Plus Thermostat Device Handler - Honeywell, GoControl, CT, Linear, Trane, MCO, Remotec

You may want to check our a Venstar system which can add an extra C wire to exiting setup without a running a new wire. FYR, the IRIS Smart Plug doesn’t act like a reliable z-wave repeater even though it’s capable, rather it is also know to cause issues with the zwave mesh as reported by other folks on the forum.

Also you can look at the CT-50 or CT-100 models which have a battery option in addition to the C-Wire