He is? Oh, you mean back in 2014, when he played a handful of games for us? Over the last two years, during which he has played very little, Dupuis has looked like an average third liner. Nothing more. And like Rob Scuderi, Dupuis will be 37 years old by the time the next playoffs begin, so he is only going to look worse from here on.
Nick Spaling is an average (or perhaps, slightly above average) third liner. And most of us here agree that at 2.2 million, he is overpaid.
If you think Dupuis at 3.75 million for another two years (almost 400k more than Scuderi) isn't massively overpaid given his role, then you haven't been paying attention.