Benjamin Olson
Hero
Um, note: There's not just manufacturing/printing costs. There's a distributor, a wholesaler, and a retailer in the typical physical book sales chain. If you buy through Amazon, you basically cut out the end retailer.
Some quick Google work tells me that for a typical hardcover book that goes for $30, the publisher gets maybe $6. The profit margin there is something like 40%.
Similar google work for e-books says that for a $15 e-book, the publisher gets somewhat over $7, with a profit margin of 75% or so.
Mind you, D&D Beyond isn't a typical e-book sale, so we may not be able to easily say how the numbers work out there.
Above numbers from varous articles int he past decade. Your searches may vary.
All fair points, though much of their sales even of physical copies are through atypical distribution (I'm guessing the local game shop doesn't negotiate prices the way Barnes and Noble does). The profit margin is probably pretty thin on Amazon, it was just the easiest place to get a sense of sales figures.
In any case the basic point is that they have several books that are continuous bestsellers with little risk and very limited ongoing development costs, the dream of every publisher. When they print another fifty thousand copies of the PHB they know they will sell, and won't have to be discounted.
The same is obviously not true of campaign books, at least not on remotely the same scale since it is usually one bought per group and interest somewhat flags off over time. Probably why they come out with a somewhat limited number per year versus other editions to heavily promote. But those are also help to market the overall game.