Title says it all: I think the Big-boy wheel's previous, pre-TT_Unstable recipe is fine, and the Behemoth wheel needs to be more expensive. The reasoning is that both wheels are both at GeoCorp Grade 3 and have high weight capacity.
This is the current recipe for the Behemoth Wheel:

This is the current recipe for the Behemoth Wheel:
- 2x Hardened Titanic
- 2x Titanic Alloy
- 1x Fuel Injector
- 1x Cyclone Jet
- 4x Titanic Alloy
- 2x Fuel Injector
- 2x Thermo Jet