Amazon Pricing Irregularities

I'm by no means the first person to point this out, but figured I'd point out a pretty serious irregularity in Amazon's pricing for a returning user compared to a 'new' user.

I was looking on the Amazon Kindle e-book store, as one does when procrastinating, and saw the following NRSV Bibles for Kindle listed for $7.99. A pretty standard price for an e-book, right? But when I clicked on them the price had almost doubled to $14.82! Naturally I went back and forth a few times, looked closer, but each time the prices in the search were $7.99 but rose to $14.82 when I clicked on the book. See screenshots from my browser below.

I've seen this on some other books, though with much smaller increases, around 10-15%, and assumed it was just a tax thing. Maybe they only show tax once you view the book details... annoying perhaps, but maybe its just too hard to cache search results and work out the local tax rates all at once... who knows. But that's clearly only part of the story (sales tax does indeed apply in my area for this publisher), because sales tax isn't 85%... it's only 10%. So where does the other 75% come from?!

Unlike some reports, this isn't just a case of multiple versions of the same book at different prices. There's no '+' icon next to the formats to show other versions; this is the same item.

So I opened up Google Chrome and went into Incognito Mode and repeated the search. I didn't log into Amazon, just checked the prices. Here's the search and item details, both showing the $7.99 price.

What the hell? If I log in and tell them who I am, they want to charge me 85% more for the same book?!

This is definitely an extreme case. The highest of the price discrepancies I saw, but its not uncommon to see a rise of 10-15% over the 'incognito' prices, when they know who you are. Another similar book from the same publisher rose "only" 14.7% (from $15.67 to $17.97), which is "only" 4% over the applicable sales tax.

This is pretty poor form from Amazon, and is pissing me off enough not to buy from them. Even the 4% increase (over sales tax) is dodgy, but seriously... 75% increase for logging in?! No thanks.