Apple monetizing apps is ancillary to their monetizing of hardware. The real accomplishment is how Apple has managed to dominate market share while competing against a gamut of OEMs with a free OS and much lower price points. Apple may not be the leader in market share going into a refresh of iPads, but that's a temporary problem and not a reflection of the trend.
One company (Apple) chooses to restrict the hardware they let their app platform run on so they can have more control over the experience.
Comparing the use of one app platform to use of a competing app platform is a perfectly reasonable comparison.