Several years ago, I compared how much I would save using (decent) margarine over over butter. It came out a few cents a week, so I decided that butter was a small luxury that I would give myself.
I've tried them all and settled on Beurremont 83%, $4.98 a pound at Zabar's, which I like as much as or a bit better than Plugra. The only superior stuff I've tried is Ecire, but it's impossible to find, and since it's imported it often has started to go rancid.
Then last week I got some Organic Valley Cultured and am a convert. It's 84% butterfat, which seems to make a difference, and the flavor is particularly good.
Alas, it's $4.49 for HALF a pound. But it's really better. . . .