I think with digital people buy at all levels, depending on their interest in the book. Personally, I buy some stuff on day of release, some stuff after a moderate price drop, some stuff only when it’s heavily discounted and there’s other stuff that I’d only check out for free.
Usually the publishers and Comixology are pretty good at judging when to discount books, and how deeply - usually at least a couple of months after publication, and often a bit more than that. You don’t want to upset people who have only just paid full price for something, and there’s also an element of not undercutting physical retailers too severely. But you want to get the extra cash from those people who would never buy at full price.
I think the reason this Marvel sale has captured people’s imaginations is that the discounts are just so deep and so soon after release. It does seem reminiscent of the previous free giveaways, but even then I think it was single issues rather than hundreds of recent collections that were being punted.