The problem with large enclosures is that it is EXTREMELY difficult to maintain a proper temperature gradient and proper humidity.

If a helix is too expensive for you then a big enclosure is not for you. You will not be able to avoid the costs of maintaining a large enclosure. You do not need a night drop with ball pythons. It is unnecessary unless you are trying to signal a breeding behavior.

A good thermostat is the herpstat or the less expensive Ranco or Johnson controls. They can all be found on reptilebasics.com.

You will be paying a lot of money for a good thermostat and heating and cage furniture.

Your best bet is going with some kind of belly heat or radiant heat panels. CHEs will sap humidity out of your enclosure making it almost impossible to keep you humidity at the recommended 50-60%.

Hope this helps!