To me "a pair of" can colloquially (see, I did it again) mean "a bunch of".
I'm with you on "couple" potentially not being exactly two, though I tend to default to using "few" in such cases. But I can't sign up for "pair" not being exactly two.
Yay language!
If someone puts on a pair of jeans followed by a pair of socks, how many articles of clothing have been put on? :)