Much to my surprise, it seems that the kindle version is now outselling the paperback version. I'm having a hard time understanding this from a rational price perspective.
Kindle version: $9.99
Paperback: $19.95, but suppose free shipping and reselling it. Here you'd have to price it at $15.50 or so in "very good" or "like new" condition to beat the free shipping. Amazon will take 15% of the sales price (or is it 10%?) and give you $3.99 to cover shipping. Reusing an envelope it'll cost $2.7 to send it mediamail. Total cost = 19.95-15.5*0.85-3.99+2.7 = $5.49.
Clearly, other considerations must be in effect here.
Because from a strict price perspective I was considering setting the price lower for the kindle for the above reason. Now it looks like I should have set it higher.