W/O knowing the VIN, prices are hard to determine.
early C280's use belt tensioner 103-200-08-70 with a list of $290. & labor is about 2.2 hrs.
later ones use a 104-200-08-70 & only cost $105. & labor is about an hour.

The drag link lists for $270. & takes about a hr to install. Plus alignment.

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