It remains to be seen if President Obama's $787 billion stimulus bill, with $17.4 billion allocated for automakers, could be the shot in the arm they need to restore flagging sales--which were down 36.6 per cent in the US in January.

Unfortunately, today's popular, downsized, fuel-efficient vehicles that promise dependability and affordability over the long-term are not the cars that translate to profits for the automakers. Instead it's the higher-priced, less-practical vehicles that make more money; they also continue to cost consumers long after they've driven off the lot.

"People need to be looking at all these various costs, such as depreciation and insurance and maintenance and repairs and fuel efficiency," says David Wurster, who leads product development and industry analysis for Vincentric, an auto-industry data analysis firm based in Bloomfield Hills, Mich. "Those always should be areas to be considering when you're purchasing a car because they separate a good buy from a money vacuum."

To wit: Most buyers will do just fine with the $98,500 Mercedes-Benz SL550 Roadster as opposed to its $190,700 Mercedes-Benz SL65 AMG Roadster counterpart. The AMG costs so much more because of its ultra-specialized, ultra-powerful engine, which guzzles more gas. Never mind that the AMG has some of the highest depreciation, insurance and maintenance costs of any car on the road.

Behind the numbers
To find the costliest vehicles to own, we used data from Vincentric to calculate the costs of depreciation; interest on the loan; fuel; maintenance and repairs; taxes and fees; and insurance over five years, then divided the results into 11 segments (excluding low-production vehicles from the likes of Aston Martin and Bugatti) to find the most expensive models in each class.

What we found is common sense: Cars with high sticker prices tend to cost the most over the long haul. German automaker Mercedes-Benz, in particular, dominated our list, with five segment winners, including the $194,950 S65 AMG sedan and $88,500 E63 AMG wagon.

But exceptions do occur. At $53,460, the Chevrolet Suburban is priced less than the $55,340 Lincoln Navigator SUV but has a higher ownership cost due to its higher depreciation rates and poor fuel economy.

Another pertinent finding sometimes overlooked by consumers: The cost of ownership far outweighs the initial price. Prospective buyers would do well to remember that the $58,400 Infiniti FX50 will have an actual cost of $85,152 after five years of paying for gas and maintenance to keep the vehicle running well.

James Clark, the general manager of Automotive Lease Guide, an auto analysis and forecasting firm based in Santa Barbara, Calif., says consumers are delaying the purchase of new vehicles and canceling altogether plans to buy less-than-practical vehicles like the cars on our list.

"The coupe, the convertible, vehicles like that, that are really more of a second or third car, have really struggled," Clark says. "At this point, it's a 'nice-to-have.' It's not a need. I think this environment is just kind of pushing people toward something more practical than those types of vehicles."

Gas guzzlers
While depreciation is far and away the greatest cost in the first five years of ownership, fuel costs are significant as well. But some cars demand proportionately more fuel than others.

The Chrysler 300 SRT8, with its gas-guzzling HEMI V8 engine (owners must pay a gas-guzzler tax on its 13-mpg city mileage), will require roughly $11,979 to fuel for five years. That's hundreds of dollars more than the fuel required for many similar sedans and coupes.

Hybrid vehicles in particular can pose a false dilemma when it comes to fuel. The Cadillac Escalade Hybrid, for example, uses thousands of dollars' worth of gas per year.

"The time to recoup that cost through fuel-economy savings alone is longer than most people keep their vehicles," says Jason Fogelman, a Los Angeles-based auto writer who maintains the About.com guide to SUVs. "In most of the SUVs, the hybrid system doesn't really have that great of fuel efficiency. It's ... not really Prius-levels of fuel economy."

The base model of the conventional Escalade ($63,155) gets a combined 15 mpg, while the hybrid version (base price: $74,085) gets 20 mpg. At a rate of 15,000 miles driven per year and assuming the current national average cost of gas ($1.93/gallon), it would take Escalade owners almost eight years to recoup the premium they pay for the hybrid version.

Expenses under the hood
Maintenance is another major factor impacting ownership costs. Buyers should always research how much mechanical attention a particular model needs before they close a deal.

If the maintenance interval is "5,000 miles, you're going to have a lot more maintenance opportunities than you would if it was 7,500 miles," Wurster says. "The fewer times you're in the shop having maintenance or changing oil, the better off you are."

Of course, most people who buy ultra-luxury vehicles can afford to spend more on maintenance as well as on gas. For them, the thrill--not to mention prestige--of owning such a high-value car trounces any qualms about the expense.

As the economy sours, however, justifications for such an expenditure tend to dwindle.

"Luxury vehicles in general have suffered some pretty significant declines in the past year as people have adjusted their spending," Clark says. "Now that the market has sort of shifted in the other direction, it's a challenge because they're so expensive compared to where it used to be."