Comment by mithr

Fair point, though I think that wording leaves room for interpretation...

Does learning your social graph by looking at email metadata (sender/addressee, location, time) count as "scan[ning] or reading your Gmail messages"? There are a lot of insights you could "skim from the top" if you control an entire communication platform, even if you don't fully dig into the content.

And regardless: to OP's larger point, the reason Google offers services such as Gmail for free isn't mostly because their support cost is low -- it's mostly because these services allow them to collect a large amount of data that is then used for selling targeted ads, far surpassing the amount of money they would earn from offering ad-free services.