In fairness to all, we don't discuss pricing on the Wall. Thanks for your cooperation.
Thermostat Clicking Noise
but the click is caused by a relay in the thermostat closing. This is what "tells" your system to start. The mechanical relay we use actually costs us more that a silent electronic switch, but it is far more reliable. If you want total silence, up grade to the VisionPro IAQ; it's relay is on the control unit that goes in your mechanical space.
However, if the stat is clicking more than once for on, and once for off, something is wrong in your system.