It was supposed to be there. The writer was likely going off an older version of the Missions Template, from which it was missing as well. Ahh well. I'd love to get it fixed and updated, but that likely won't happen till after Gen Con at the earliest.
As for the discount... It's justa discount, you still need to obtain the item, and it's only items that the faction rep can actually get. So Joe Martin isn't likely to be able to get you Military Grade hardware. But, keep in mind that there is the handy dandy, quick 'n easy Obtaining Items Through Contacts rule in the FAQ, where you can get an items of Availability equal to 4x the Contacts Connection Rating. And the contacts in Season 4 aren't lightweights. And for just a few nuyen more you can buy additional Availability (aka, 5% extra per point). Each contact can get you one item (or group of the same items) during a single downtime period (Minimum Downtime is 1 week).
Also, as a note, the Faction Rep Chart is on the SR Missions website as well, at
http://www.shadowrun4.com/missions/gamemasters/Bull