by any reasonable metric you choose Valve is at best as deeply invested in MTX
Completely agree with this. I honestly believe the best apples-to-apples metric is to look at their most popular games and compare the mtx across them, in which case Valve doesn't exactly come across as good in the comparison.
In terms of publishing, with the exception of Aperture Hand Lab (basically a little tech demo), they haven't published any third party developer's game since 2010. For the purposes of this conversation, I think it's fair to count EA subsidiaries as EA.
When you make no games you make no MTX
Absolutely, this was the counterpoint I was trying to make about the raw "number of games" argument.
EDIT: Oh, I see the misunderstanding! I mean "published" as "financially backed the development, advertising and releasing of the game", not "published to their storefront". Same word with multiple meanings can be a major source of misunderstandings.