SD cards may all look alike, but they vary. Fast versions of the latest standard, SDXC, are the priciest, but you’ll still pay for speed in high-end SDHCs. The higher the class—the highest being 10—the faster the card. No listed class or max speed? Beware—no telling what you’ll get. Click through the gallery and find out exactly why some cards are more or less expensive than their counterparts.