Rear strut replacement: 04 Ford Taurus?

A mechanic recommended getting my rear struts done because one of them is shot and leaking oil. Said each strut would cost $180.
I found a pair of complete strut assemblies on a website, brand-new, for sale for $140 total. Completestruts.com.

Is this deal too good to be true? And if I get the parts online will a mechanic still install them for me?

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