Sometimes the rebranding is a good thing. Let's take for example tap & die sets. The Matco set is sourced from Irwin. The Matco pieces carry a lifetime warranty & the Irwin do not. Are they more expensive? Yes. Is the expense justified? That's up to the buyer to determine.
I probably would have never bought these Sunex/Matco items from Amazon or wherever; as I would have never known about them. I had a credit from Matco, and was browsing their catalog, and thought ...now that's a cool tool. So the idea that Matco can turn you on to certain private labeled tools is worth something. But their mark-up is obscene no matter how you slice it.
I do see your point with respect to the Irwin Tap and Die sets, (which it seems EVERYONE is private labeling these days). But while Matco's selling price is close to Irwin's list price on those sets, the Irwin sets typyically sell for at least 50% off list. That difference represents a LOT of replaced taps, especially since the ones most often broken are the smallest, and cheapest ones of the set. But it certainly is nice if you have a Macto guy bringing replacements to your door; definately worth something. BTW....aren't those Irwin Taps & Dies now made in China???? Far from my favorite tap/dies anyway.