This may be a duplicate of Why is renting a car through a broker cheaper than directly through a car rental company? but I don't think the answer addresses a really large price difference.
I rented a car last week in Germany. Prices were unpleasantly high everywhere so I looked into third party providers, in this case "check24.de". They came in at less than 40% of renting the same car at the same company directly (Alamo in this case). Other brokers were offering similarly good deals.
I went for it, figuring there was enough margin to cover any hidden fees, surcharges and scam attempts. To my pleasant surprise, everything went great: my reservation was on file, already connected to my Enterprise Plus account (apparently there was a merger) and I even got a nice upgrade. Drop off was equally efficient and the total price paid was exactly what was originally advertised.
Question: How can a broker offer a 60%+ discount for the "exact same" car/company?