It's always important to know what you are getting yourself into when purchasing a used car, and sometimes buying a premium used car sounds like a better alternative than getting a brand-new mid-range car. After all, who wouldn't want to drive top-tier luxury at a Toyota Camry price? But IntelliChoice's list of 2011 premium used cars to avoid this list points out just why these cars may not be worth it.The list really struck us for two reasons. First, there are only three manufacturers on it. Second, it's dominated by one manufacturer in particular: Mercedes-Benz. It seems that buying a used Benz just isn't worth it, if these results are any indication.All results have been based on what the projected cost of each vehicle will be over five years. The vehicles listed below all raked Below Average or Poor in the Cost of Ownership calculations. There were six fields of costs that were examined, which are fuel, insurance, depreciation, used price, repairs, and maintenance. From these criteria, the following vehicles have been found to be too costly in the long run.