Be sure it's a thermostat and not a rheostat (which is essentially a dimmer). Thermostats will keep your temps at a consistent temperature, adjusting accordingly to room temp fluctuations.
Rheostats you will have to monitor and manually adjust throughout the day (and night) as the temperatures in the room change.
It seems like a bitter pill to swallow to spend $80 on a quality thermostat from someone like Reptile Basics, but given the lifespan of your snake, the longterm cost is pennies a day (not to mention, preventing burns on your snake, which would lead to veterinary expenses).