These are just shock absorbers, not struts. They are not difficult to replace. Even at 1 hr per shock, this would be less than $900(assuming $100 per shock). I would guess the real time is closer to .5 hr. $1600 is a major rip. The shocks do cost about $100 each. Go back and ask for a parts/labor breakdown. They are charging way too much for the shocks and/or the labor. If DIY(which is really the best course of action IMHO) is not an option, find a different shop. Remember, you could buy a whole lot of tools to help your DIY projects for the money you'll be paying someone to do this. If you do it yourself, the tools are free.
Good Luck, Dan

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2012 E350 Bluetech