David's a hardcore coder and a talented technologist, for sure, but... well, he believes whatever he believes at the moment very strongly. He has a very solid reality-distortion field.
As an example, he really believed it was fine to have mechanical turk freelancers see people's receipts. He would say something to the effect of "people throw their receipts in the garbage where any sanitation worker can see them - this no different." I wasn't around when the mechanical turk stuff made the news, but it seems like it caught him totally off guard that people would be upset.
I suspect that the conversation around the price increases went something like:
David: There, I just sent a 3-page-long plaintext email explaining our price updates to everyone.
Other Expensifier: Shouldn't we notify people who have opted out of those emails?
David: If they opted out of announcement emails, they don't want announcment emails. Seems straightforward to me.
Other Expensifier: Yeah, but, like, we don't have multiple opt-out channels. They can either get every multi-page plaintext missive you send, or they can opt out and miss significant price increases.
David: Nope. They made their choice, we should respect it. Multiple opt-out channels are an antipattern. Anyway, the number of users who will be upset about this are vanishingly small - let's worry about the rest.