I've no idea, to be honest. However, there's also a pricing issue. The print versions are priced at "cost" so that they make us exactly the same amount of money as the PDF. We don't charge any extra for them other than our costs. By selling a reduced cost version, we're therefore effectively
paying out for the privilege of you having our book. In the long run, if we were doing that, it would be more to our advantage if you didn't buy our book - it would save us money!
On the other hand, giving away a free PDF with the print copy costs us nothing at all, so there's no reason not to do it.
The basic problem comes with a fixed per-unit cost to produce one (the print version) and no cost to produce the other. So we can play around all we like with the PDF version, but reduce the print version by even a penny and we're losing money. It's already priced exactly as cheaply as we possibly can.
My guess (and I don't know for sure as I wasn't involved) is that the Ceramic DM book, being a zero-cost product in terms of production, allows for a lot of fiddling with the numbers.
At least that's how I understand it. I'm not actually directly involved in this sort of thing, so Hellhound can feel free to correct me or tell me I'm talkng rubbish!
