In most cases, it will cost you more to purchase a new CD than it would to buy that same music as an mp3 download. Which makes sense, since digital files don’t have the high manufacturing, shipping, or storage charges that physical discs do. But sometimes, you could end up on the short end of the stick if you just assume that the mp3 will be cheaper.

Above is a decent example, sent in by Consumerist reader Jeremy, who noticed that while Amazon is charging $11.99 for the digital download of David Bowie’s new album, The Next Day, the price for the CD is slightly less — $11.88 — and it includes Amazon’s Auto-Rip service, that automatically places a digital copy of the album in the customer’s Amazon account, making it available for streaming or download.

Of course, if you’re not an Amazon Prime customer, or you live in a state where Amazon collects sales tax, then that savings goes out the window, as you’ll be hit with both shipping and taxes on the CD that you probably wouldn’t be charged if you purchased the mp3 files.

Basically, it’s just another reminder to consider all your purchasing options and to never make assumptions about the relative affordability of one format over another.

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