It's not every year, and if you look around, you'll see optical drive failures are common across the entire industry. Not sure why this is always such shocking news to people, but whatever. Optical drives fail, and fail often. Doesn't matter if they're the slot loading kind Apple prefers or tray loading like most everyone else uses, they fail. Usually based on how much they're used, and the condition of the media you put in them. You put a bunch of really nasty looking discs inside the thing, what would you expect but that the focusing lens for the laser gets coated with crap? Then again, sometimes drives can just up and die.
It can also make a difference on where you go to get your system repaired. Some places, and if they're an AASP they're not supposed to (and will get into some deep **** with Apple if caught), will buy parts off of dumpster diving vultures like MPD and Blue Raven. These companies buy up excess inventory from repair shops, and will buy up uneconomical to repair units from retailers like Fry's and Best Buy, then break them down for their component parts. Most of the time the parts are already on their last legs, and fail pretty quickly, but people buy them because they might be a few bucks cheaper than getting one from Apple. It gets even better, in that a lot of times a particular part has to be sent back DOA multiple times before these companies "retire" it. There's also frequent issues in getting them to send the correct part from what I've seen.
I know in the past, where I work, they used these companies before, and a good chunk of my job now revolves around cleaning up that mess. Pulling and replacing those parts as I find them. We have other arrangements with Blue Raven that don't involve Apple, and let's just say that they are not exactly what you'd call a well run company. Shame I'm bound by some confidentiality agreements, because they are some really good stories.
Anyway, I digress. Point is, optical drives fail, and fail often. Laptops are always going to be more expensive to fix because the hardware is much more custom made. I'd bet if you take a look around, replacing the optical drive in a Dell or HP laptop isn't all that much different in cost from Apple.