Walmart In Store YMMV
Picked one of these up last night for $68
Checked Brickseek and some Walmarts in the area have them as low as $65
These are supposed to be compatible with about 85% of HVAC systems.
You can check compatibility here:
Also worth it to check what county/state energy programs are available to you, my wife and I are eligible for a $50 rebate through our county making this a very cheap upgrade for our house.
my first post, hopefully I did this right