It certainly is a bargain. D class is $3906 r/t a/i, certainly not what you're looking for but 6 months ago it was only $2219.

The rules for the I fare are here: http://matrix.itasoftware.com/#view-...2;fare-key=0/0

BTW everyone uses it as you do, as shorthand for the business cabin, but "J" is the class code for the most expensive unrestricted tickets in the biz cabin.