Serious car collectors are forced to spend tens of millions of dollars to be the next custodian of the most valuable cars on the planet. Many things can contribute to the value of a car. A low production number, outright rarity, aesthetic design, originality and purity of the example. History, previous owners and provenance will also often come into play, driving up the price of otherwise less important cars, but can also make already expensive cars even more so. The following are the most expensive cars to be bought at auction based on the adjustment for inflation.

1962 Ferrari 250 GTO - $48,405,000

The Ferrari 250 GTO, serial number 3413GT, sold at the end of August 2018 for $48,405,000. The sale took place in Monterey, California but caused jaws to drop all over the world. The 250 GTO is the international car collector's holy grail. It was sold by Greg Whitten, a former Microsoft executive, who bought the GTO in 2000. It's not confirmed how much he paid for it then, but it's believed to be just under $5,000,000. This one has everything it needs to hit that price, including a serious racing pedigree. It may not be the most expensive sale of a 250 GTO though as one is rumored to have sold for $80 million through private hands in 2018.

1962 Ferrari 250 GTO - $40,338,000

Until chassis number 3413GT went on the block, chassis number 3851GT held the record for an auction sale. It sold for $38,115,000 in late August of 2014 through Bonhams in Carmel, California. Only 33 true 250 GTOs were made, and all came powered by a 296-hp 3.0-liter V12 engine. This particular one was raced internationally, including the World Sportscar Championship from 1962 to 1964.

1957 Ferrari 335 S - $37,281,000

Ferrari sweeps the podium thanks to this entry: a 1957 Ferrari 335 S sold in Paris for $35,730,510. Only four examples were built, and this one was in good condition and boasts serious racing pedigree, including a stint in America with Luigi Chinetti's North American Racing Team. Unfortunately, it was also involved in the crash that ended the iconic Italian Mille Miglia as a competitive race. Driver Alfonso de Portago was at the wheel and the crash killed him, his navigator, and nine spectators.

1954 Mercedes-Benz W196 - $31,837,000

When it comes to historical pedigree, being the car that the legendary F1 driver Juan Manuel Fangio used to achieve his second Formula 1 championship in 1954 is an immense value-add.

Before going into private hands though, the 1954 Mercedes-Benz W196 was restored and displayed in the Mercedes-Benz museum, but its value didn't end there. It was then used for tire development and testing, and the chosen weapon for the legendary Mercedes-Benz engineer, Rudolf Uhlenhaut, who kept the car for his exclusive use. It sold at Bonham's Goodwood auction in the UK for $31,837,000.

1956 Ferrari 290 MM - $29,649,000

Scuderia Ferrari Works racing cars are incredibly desirable, and the 290 MM was a true Ferrari factory weapon of its day. Its first outing saw a second-place finish at the Mille Miglia race, and this one was driven by legends including Juan Manual Fangio, Sir Stirling Moss, Phil Hill, Peter Collins, and Wolfgang von Trips. It raced all over the world but was sold in full 1957 Sebring race spec and colors, Sebring being the last place it was raced as an official Scuderia Ferrari car. It was sold in New York by Sotheby's for $28,050,000 in 2015.

1967 Ferrari 275 GTB/4*S N.A.R.T. Spider - $29,578,000

In 1937, an orphan named Eddie Smith landed in Lexington, North Carolina with just $15 in his pocket. He found a low paid job but ended up building an immense mail-order business. And buying Ferraris, including one of the 275GTB/4 North American Racing Team editions. 25 were meant to be built, but only ten were eventually made due to a lack of actual demand. Steve McQueen liked it though but managed to wreck his. Smith continued to drive his, raced it at Sebring, and all the while it grew in desirability.

"I bought it for the right reasons and kept it for the right reasons. Because I really love it. I feel like it's a part of me," he once told Ferrari driver, Phill Hill. After his death, his son Eddie Smith Jr. sold the 275 GTB/4 as he felt it was being "imprisoned" in a hanger. On August 17, 2013, bidding started at $10,000 and ended at $25 million. Smith Jr. then announced the proceeds of the sale would go to charity.

1964 Ferrari 275 GTB/C Speciale - $27,940,000

The sixth Ferrari on the list sold through RM Sotheby's at Monterey in August 2014, the same time as the second-place GTO. It went for $26,400,000. It was the first of only three Works Berlinetta Competizione cars built and actually rarer than its 250 GTO siblings. 453 units of the 275 GTB were built for consumers, but only three 275 GTB/C Speciales were put together, specifically to run in the 24 Hours of Le Mans in 1965.

Those that remember their history will know that's the second year Ford brought the GT 40 to Le Mans and Ferrari fielded 12 cars in total. This was the first 275 GTB/C Speciale built but, curiously, never ran.

1956 Aston Martin DBR1 - $23,049,002

In 2017, one of the most important Aston Martin race cars built sold for a new record of $22,550,000. Its importance was down to the fact that chassis number DBR1/1 was the first of five DBR1 models built by David Brown (whose initials are the DB in the name) to win the 24 Hours of Le Mans in the 1950s. Chassis number 1 never won Le Mans, although another DBR1 did. However, this one had a very lively history racing at Le Mans, the 12 Hours of Sebring, and the Nurburgring 1000KM, of which it won in 1959.

1955 Jaguar D-Type - $22,737,329

The Jaguar D-Type wasn't just an incredibly effective racing car, it was also beautiful to look at and rivaled the Italian cars at the time. Except, it also beat them at Le Mans in 1955, 1956, and 1957.

Chassis XKD 501 sold for $21,780,000 in 2016 and was the car that took the title in 1956 after a close race with Aston Martin. It was entered by Ecurie Ecosse, a non-factory team, which is why it's painted in traditional Scottish Blue with a white cross rather than a form of British Racing Green. Its well-documented history and rarity make it the most expensive British car to be sold at auction.

1935 Duesenberg SSJ - $22,000,000

Only two Duesenberg SSJ models were built, and this one originally went to the Hollywood star Gary Cooper on a 6-month loan to generate publicity. Cooper liked it enough to buy it when the loan period was up. Its original color is unknown but suspected to have been a sand color that Cooper's wife didn't like, so it was painted green with silver trimmings. It's had several owners since Cooper, but that's the big-ticket name. At some point, it ended up in the collection of Briggs S. Cunningham and painted in the two-tone gray it is now. A fierce bidding war at Pebble Beach saw the car sell for $22,000,000, which makes it the most expensive American car ever sold at auction.