Interesting Problem: Two Unconnected Dashes, One Phrase

What's the whole sentence?

As Bufty said, without a little more context, it's hard to say. But my initial reaction would be to render this phrase as "not cost-correlated" rather than "non-cost-correlated". That might require a little rewrite of the entire sentence, but shouldn't be difficult to do. If it is a problem to rewrite, then you probably have bigger issues than just this phrase.

caw

An en dash is used for a hyphenated compound where one of the parts of the compound is more than one word. So you could do: non–cost correlated. Other examples when you'd use an en dash: "Pulitzer Prize–winning," "New York Times–bestselling," etc.

This is CMOS FAQ is a good discussion of the en-dash; it's primarily used for ranges.

The older custom of using an en-dash for a prefix used with an open compound is fading; most typographers just use a hyphen.

A traditionalist would set non cost correlated with a leading en-dash:

non–cost correlated.

Cost correlated is not normally hyphenated; non is a prefix particle, so a traditionalist would use it with an en-dash and not a hyphen. But honestly, that's very old-school.

But I suspect given the context, I'd go with blacbird's suggested rewrite.