It's clear it's not free in the title
The title says Kindle. It costs money to buy things from the Kindle store. If not, it would've said PDF and figured if you had a Kindle you could put it on there yourself for free. I think it was clear enough and is fine. I like that Ars Technica and The Register are both experimenting with ways to add to their bottom line this way. Less chance I'll find a 404 message the next time I come over here for a bit of free reading.
The Fail is for you Failing to understand that they were selling this for "actual money" as you say. Maybe they should've taken bitcoins?