The thermostat is the single most important item you can invest in. I don't know what your collection looks like but imagine you are about to hatch out a clutch of leopard enchi clowns worth about $3500 to $5000 apiece. Do you really want to be that guy that saved $30 bucks buying a cheaper thermostat and then lost a clutch of eggs worth potentially $15,000 to $20,000 dollars. Lets take another direction. For the sake of 30 or 40 bucks, do you want to risk potentially losing/killing 6 to 10 baby ball pythons regardless of the morph/value.
Buy a good proportional thermostat and it will give you piece of mind and last you years. I like Herpstats but there are others that are still quality.