I can't find a source for the price-matching clause (I'm on my phone, sorry) but have read it several times. The lower-priced keys typically come from cheaper markets/regions (e.g. Russia), which AFAIK is kind of a grey area depending on jurisdiction, or from time-limited offers.

I base part of my reasoning on this article, where the author points out there are already cheaper options with good tooling such as itch.io, yet they do not attract a lot of titles: https://www.fortressofdoors.com/so-you-want-to-compete-with-...