Yes... cost... certainly a problem for people of upstanding moral fibre. So I'm told.
Yeah, at half the cost of a Codex in CAD, it's a great value. Though I'm not fond of digital products myself, a paper copy is just another $15 worth of ink and paper.
That said, I was quite impressed with the Mont'Ka book. If I wasn't suspecting a new Guard codex in the next 3 months, I probably would have bought it. Which is saying something, for me these days.