You don’t leave money on the table as a business. Period.
That's a terrible approach that ensures your business ends up with absolutely no-one trusting or liking it, and that (soon-to-be-ex) customers expend effort on actively seeking alternatives, rather than returning to you as a matter of course. It's a great way to be very certain that you go out of business the very moment there's an alternative to you - here they have a bit more of an opportunity because it's effectively a monopoly, so it's harder for them to end themselves that way, but ruthlessly sucking every dime out of the customers at all costs is an extreme short-term-ist way of thinking. However, despite their monopoly, I can't help but think they may simply find increased piracy rather than increased sales - this sort of thing often backfires by forcing normally-passive/impulse-buy customers to suddenly reconsider what they're doing.
A great example of this would DLC for the videogame Total Warhammer 3 - they'd been selling DLC at a fairly set price for several years - and whilst there was the usual moaning at the start, people had become completely acclimatized, and were they were getting huge sales from people essentially just buying DLC without thinking about it, because the value proposition had been so well-established. People didn't stop and think "is this DLC worth it?". But then they decided to hike prices, and like these, by significantly more than inflation, and when their actual costs of production for the DLC weren't any higher (which is also the case here - they're simply asking for more money for existing often poorly-scanned and imperfect PDFs - they're not doing high-quality rescans or the like, which could potentially justify this). The logic seemed to be that, if they hiked the price by X, but lost Y copies sold, then as long as X was high enough (please don't make me do the actual formula), they'd still be making more money - especially in the longer-term.
Except they didn't consider how this would be a "shock to the system" of the previously passive consumers, nor the "sticker shock" factor. Not only did they not sell enough copies, even with a large price hike, to justify the lost copies sold, but they saw sales of DLC decline generally, as customers re-assessed whether they were worth the money. To be clear, this wasn't some organised boycott - that never works with videogamers, too many of them are emotionally incontinent teenage boys (or men in their 20s/30s/40/50s/60s etc. who just act that way!) - but by doing this, they profoundly wrecked the nice scheme they had going. And they lost a huge amount of trust, pretty much permanently - they've made multiple apologies and significant efforts to try and regain that trust, but if you blow this sort of thing up, it's not easy to fix.
WotC will probably get away with this particular thing simply because DriveThru is so niche and not well-known, but it's a case of just barely getting away with it, not a smart business practice as you seem to be suggesting. It will damage the loyalty and trust of the existing customer base, who are pretty niche anyway, but WotC probably don't care because really in the longer-term I suspect they'd like to kill off DM's Guild in favour of a fully in-house store where they can take 100% of the profit, not 50%.
I mean, hell, talking about "NEVAR LEAVE MONEY ON TEH TABLE!", you remember the OGL 2.0? Remember that? That was about not leaving money on the table. Turns out that money really needed to stay exactly where it was.
