Gillette probably knows that the average Fusion user will spend more than the average shaver. There's no indication that this data applies only to men using Fusions or other expensive cartridges. If it's an average of all men, then it probably includes users of cheap disposables and the cheaper cartridges. It might even include the injector, SE, and DE users here, averaged in with the people who use more expensive cartridges.
My personal experience with a Fusion was that, after the fifth shave, it was feeling a bit rougher, and I didn't want to push it more than that. I can imagine that maybe I would have gotten another couple of shaves from it, but no more, so there's no way I'd do it for $23 a year.
If I were still using my Personna Atra style cartridges, I'd be paying about 50¢ each for them and using about 1 a week, for about $26 a year (I'd probably be shaving only five times a week instead of every day). Some quick estimating tells me that it could probably cost less than $20 a year for Bic disposables, and less than that for DE users, of course. So on average, Gillette's data is quite plausible.
"...when I attempt a discourse the words come out as they will, and they may make sense when they strike the atmosphere, or they may not." O.Henry - - "Cabbages and Kings"