After receiving an initial estimate of $2,326.53, they walked out with a final bill of $11,989.12.

The E92 BMW M3 is something of a unicorn in the M3 lineage, and it owes that status to one very special feature: its naturally-aspirated V8 engine. This generation marked the first - and only - time BMW's engineers squeezed an eight-cylinder powerplant into an M3, creating a beast with 414 horsepower. Add to that the option of a manual gearbox and a factory Competition Package, and you've got a car that's truly the stuff of enthusiast dreams.

This particular example? It has all of that, plus a service history that reads like a cautionary tale, including one outrageous dealer visit that ended up costing nearly six times the original estimate.

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Let's start by taking a closer look at the car itself, which recently crossed the auction block at Cars & Bids. The 2011 M3 was the only E92-generation model available as a four-door sedan with the Competition Package available. As such, this example has 19-inch staggered wheels (meaning the wheels and tires are wider in the rear than in the front), a 1-centimeter lowered suspension, dynamic stability control and multiple suspension settings.

Interestingly, none of that stuff led to the expensive repair bill that we're focused on here. Instead, it appears that an oil leak led to most of the problem. According to paperwork from BMW of Riverside, the car initially rolled in for an oil leak and some minor issues with the TPMS sensors back in August. What followed was a rapid escalation of work - and costs.

Initially, it appears as though the dealer started out by replacing the engine air filter, brake fluid, spark plugs, cabin filter, oil filter, and engine oil. Nothing too shocking there. They also tacked on some labor charges, likely for tracking down the source of the oil leak, a small price to pay for peace of mind. But that was just the beginning.

By the time the tech had finished "recommending" services, the list had ballooned to include new valve cover gaskets ($2,665.65), new power steering hoses ($1357.94), fresh rear tires ($1,070.16), TPMS sensors ($1,198.96), and a full rear brake overhaul with pads and rotors ($1,986.21). When all was said and done, the total bill came to a jaw-dropping $11,989.12. Ouch.

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Now, it's worth remembering that this kind of price tag isn't unique to BMW cars. After years of running a service repair shop, I can personally confirm that some owners spend copious amounts of cash on cars in excess of their value. Still, this is a great example of how much more expensive some types of cars can be and how much more one might spend at the dealer when compared to doing a job themselves or at an independent shop.

The V8-powered M3, with 108,300 miles (173,810 kilometers) under its belt, ultimately sold for $34,750 earlier this week. Considering all the recent - and rather costly - maintenance it's had thanks to its previous owner's wallet, that final price isn't half bad at all.