Don't think that's THE gauge... I just grabbed a random one to illustrate the story
Despite the tempting lure of "FREE!", I already have a couple of gauges - so I wouldn't bother going for another one.
But I have to think the marketing is smart: I bet the type of person who would agree to attend a let's say 5 minute seminar just to get a FREE! tire gauge will also be the type of person to actually put the knowledge gained (not to mention the FREE! gauge) to use and save some fuel.