I've been searching around for some rechargeable 36V battery packs and I can't seem to find one under $200. I found drill batteries are inexpensive and are 18V with 3AH. On top of that I wouldn't need to buy a charger. I could get 4 18V 3AH batteries for around $70. The only thing I'm worried about is that they might not be able to supply the amperage needed to the motors. They seem pretty powerful considering that the drill motors have pretty high torque. Do you think they can supply the amperage necessary to power the two 36V 190KV motors, or do drills just have a really good gearbox that creates most of the torque?
Electric drill motors are geared down to give high torque at relatively low speeds.
You don't give a specification for your motors. But it looks like they draw tens of amps (for example one listed on Amazon draws 24 to 65A. Four battery packs wired in series/parallel only gives 36V 6AH.
Your batteries are only going to last a few minutes at that current, as they will be grossly overloaded. There's also a risk they will overheat and catch fire.