There are no legitimate repacks. Plain and Simple.
What some shops do, which is legitimate, is cracking and entire box, pulling out the high end rares and mythics, and replaces them with bulk rares. Then they repackage the box as best they can and resell it as a $30 draft set with full knowledge for the customer that there is not value in the packs so that you're purchasing solely a draft experience at a discounted price.