You cannot get that information BY DESIGN. You also can't go to the dealer's auctions -- they are dealer ONLY.
They do not want you to know how cheap they buy cars at auction -- it's REALLY cheap, you'd be shocked! -- and how high they sell them. The markup on used cars is extraordinary -- it's many times higher than the markup on most NEW cars.
Most people (wrongly) believe that dealers make their money on the flashy new cars, and sell the used cars as a sideline. WRONGO. The used cars are the real money -- they sell for thousands over what the dealership paid. The new cars can sell for as little as $500 over dealer cost. (Sometimes with specials, less.)
They also make a goodly share of profit from selling financing. But the real money is in used cars.
If you knew the dealer paid $7000 for your car -- even after he put in $400 to clean it up, detail the interior, fix a few dings -- you'd NEVER EVER pay $14,999 for that car.
But you will. Because nobody will sell YOU that car for $7000.
Where do the auction cars come from? Sometimes repos, but mostly they are trade-ins -- acquired for almost nothing. The dealer's OTHER BIG PROFIT CENTER is totally cheating you on your trade-in -- confusing the trade-in price with the new car price, until you have no idea what you really paid.
In most cases, the dealer is actually acquiring your trade-in for NOTHING -- zero -- or close to that. They will give you a few hundred dollars for a car with a book value of several thousand. (I was just offered $700 for a 2001 minivan, with 103,000 miles which has a trade-in value on Edmunds TMV of $2400 and a retail TMV of $4200!)
Then they send it to auction and make a quick solid profit -- usually 3-4 times what they paid, sometimes lots more. THEN someone buys it, cleans it and marks it way up and that's how you find a car that a dealer got in trade for $700 and the car is marked $6999.
AND THEY GET IT. Because we have no options. Nobody will sell US cars for $700. SO we must pay $6999 and plead for a few bucks off, or financing.
That is why the car selling business is a giant multi-BILLION dollar business -- profiting hugely off the misery (and debt) of tens of millions of American workers.