In this instance, upgrade implies that you are eligible to get better merchandise for the same price (ie pay for regular headphones [1 item] and get the headphones as well as a set of mp3 earbuds [2 items] for no additional cost.)

Hey .. Here ,it's a technical word I believe ,it's probably related to a certain application on your device or something! .Upgrade here comes as a verb ,and it means to replace an older version of that "Application ,system" with a newer one (Supposedly ,improving it!! ).So ,they say that "now ,you can afford (capable to pay! ) to upgrade that system "app" etc . In Persian (Farsi) ,upgrade as a noun ,I think it's like saying (ارتقاء) . but mainly ,for a software ! .lol Hope I helped ! .All the best .