If you're going to be breeding ball pythons, I'd argue that thermostats are one of your single most important purchases, ESPECIALLY when you buy one for your incubator.

I would recommend buying a Helix or Herpstat for your incubator (over $100 each) and the Ranco or Johnson's should be fine for your racks.

Don't go "cheap" when it comes to thermostats, you could end up paying dearly for that decision. JMHO.