Unfortunately we live in an area that has little to offer than Morton's Kosher salt, so can't weigh in on the differences in salt. Of course, I could order via Internet but, at this time, it's not high on my list of priorities.
As for the salted butter issue, I can definitely tell the difference between salted and unsalted butter. Even the less expensive "house" brands.
"As a girl I had zero interest in the stove." - Julia Child
This is real inspiration. Look what Julia became!