system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: how do car dealerships make money when they claim the markup on new cars is only a few hundred dollars?
gpt
They can make money three ways when they are selling you a new car, the dealer markup, and any hidden incentives from the factory.    
The second way is what they offer you for your trade in.      
The third way is through financing of the vehicle.   They secretly get kickbacks from certain finance companies depending on what rate they offer you.   Say, hypothetically, you qualify for a 3% rate, but the finance manager will offer you a loan for 4%, so then the dealership gets a kickback of $500, and if he gets you on the hook for 5%, the dealership gets a kickback of $1000.   

So the salesperson will usually chat you up and try to pull details about what you want out of the deal, they find out what your "hot buttons" are, and lets say you demand to get $5000 for your trade, when it's only worth $4000, well then they can jack up your interest rate by two percent and make that back up.    
Or, lets say you demand a certain interest rate, so they agree to that, but the amount of money they will give you on your trade-in just went down.   
Since usually people only have one hot button, it's easy for them to find out what that is and then structure that accordingly.
So it's all a big shell game.   You ask for something, they concede, but make it up elsewhere.