Fun experiment, but it isn't as much of a gotcha as people here think. They could have verbally tricked a human customer service agent into promising them the car for $1 in the same way but the end result would be the same – the agent (whether human or bot) doesn't have the authority to make that promise so you are walking away with nothing. I doubt the company is sweating because of this hack.
Now if Chevrolet hooks their actual sales process to an LLM and has it sign contracts on their behalf... that'll be a sight to behold.