Sorry to use your thread for a rant, ailie, but you asked about cost.
I've just read "The Bodies Left Behind" by Jeffery Deaver.
In paperback, It costs £4.66 from Amazon. That covers the typesetting, artwork, printing, materials, binding, distribution, and final delivery. What's more it's now mine to do with as I please. I can give it away, lend it to friends, sell it, donate it to charity.
The Kindle version costs £6.99. That covers typesetting, and distribution via the Internet. I can read it on Kindle. I can't lend it out, give it away, donate it to charity, or sell it. If JD's publishers should ever get in a dispute with Amazon, it can be removed from the Kindle without so much as a by-your-leave. It's not mine.
When we made our software available for download, we (like most other software houses) were able to drop the price by over 50% compared to distribution on physical media. Amazon, on the other hand, mark up the price by over 50% for a similar setup.
Where I come from, we define this as a rip-off.