That rate is actually pretty good. According to this page, http://www.wireless.att.com/learn/international/roaming/affo... AT&T sells a 120-MB international roaming data package for $30/month. That implies an effective download charge of $4.55 for an 18.2-MB file.
Now if Amazon's data charge is $2.82 in the UK, where they do significant volume and the wireless market is competitive, imagine how much higher it must be in less developed countries where the company has less pull. I got charged approximately $800 for 40 megabytes of data usage in Lithuania last year, where AT&T did not have a partnership with any local carrier. I talked AT&T down to about $400 but they would not budge beyond that.
And think about the target audience for this book. Probably a lot of people spread out all over the world. It might not take all that many downloads in places like Lithuania to push the average delivery fee up to $2.48.
The only problem I see is that, arguably, Amazon should give authors the ability to opt out of paying for international downloads, or let them set different prices in different countries.
But it seems that the current delivery charge is pretty good - certainly it's not the enormous markup the headline claimed.