I don't buy a lot of pasta, so can't speak directly to that example, but in many cases if you compare like quality, Costco will tend to be cheaper or equivalent, I've found. Although maybe for some of the staples there just isn't really that much difference in quality.

There is also the problem that some folks have (cough, me, yes, I'm talking about me) that even if I go into Costco for 3 specific items, I walk out with 5-10 at least. That's another place to watch for cost and try to be strict about sticking to a list.