Give the step-by-step reasoning process and then the final answer. Liz sold her car at 80% of what she originally paid. She uses the proceeds of that sale and needs only $4,000 to buy herself a new $30,000 car. How much cheaper is her new car versus what she originally paid for her old one?

Show your work and conclude with the exact phrasing "Therefore, the final answer is [answer]." where [answer] is just the final number or expression that solves the problem.
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If Liz needs only $4,000 to buy a new $30,000 car, that means she has $30,000 - $4,000 = $26,000 from the proceeds of selling her old car. If she sold her car at 80% of what she originally paid for and sold it for $26,000 then she originally paid $26,000 / 80% = $32,500 for her old car. If she paid $32,500 for her old car and the new one is $30,000 then, the new one is $32,500 - $30,000 = $2,500 cheaper.
The final answer: 2500.