The price is next to nothing, at least in my country it's less than a beer in one of the better bars. I got compromised once and skipping one beer is definitely worth it. The costs for Blizzard to develop and send them out(free shipping) makes the price of 6.50 pretty liveable. Its the community's fault that we need the authenticators, because of our dear fellow players buying so much gold farming didn't net the sellers enough gold to sell for a profit, considering todays price for gold. They were forced to find a new way of earning gold fast, and simply stealing from others turned out to work well.
Now, if people 1) Stopped being so damn lazy and earned their own damn gold and 2) Stopped being retarded when reading their email and suring the web, making account theft an attractible way of getting gold to sell, thus making them innovative in new ways of getting to our accounts, we wouldn't need to spend the money on extra security, but because people ARE lazy and stupid, we need authenticators. Stop blaming Blizz, they do their best to enhance our security and reduce the price of the authenticators as much as possible(pretty sure they go in minus on those, really...), blame gold buyers and stupid people for making account theft attractive. If it wasn't for those you wouldn't have to pay to pay to play.
I got compromised once, for the record. WoW-heroes had a bad ad. Yea, WoW-heroes. Had to use three different spy/malware scanners before I got to the trojan and removed it(malwarebyte's anti-malware did the job). Staying safe on the internet kept me from getting compromised for two and a half years(although that's a bad argument really, they haven't stolen accounts in such a scale for 5 years, you've just been lucky after they really got started on mass theft), but then they got me with one of their more special traps. Bought my authenticator as soon as I got my buy-stuff-online-bank card. No, authenticators aren't 100% safe, but it's the safest you can get. I wouldn't have been compromised. Look here, I made a list of people getting hacked:
Stupidasses - bad internet security and virus programs, hang around at goldselling websites, buys gold, opens weird mails telling them their account is under suspension and getting checked, that they've recieved a beta key and needs to go to this-fake-site.net etc from
wow-blizzard-beta-suspension-ramming...tt@hotmail.com. (Not necessarily all, but some). This group gets compromised A LOT.
Clueless - None or weak internet and computer security. Doesn't necessarily intentionally go to bad websites, but won't check if the armory, battle.net or wow-heroes he googled his way to(many very casual players won't know exact links by heart and might google just out of habit) or got in an e-mail has the correct link, thus ending up on eu.woowarmoy.com, accidentally getting a keylogger or putting in his name and password. This group gets compromised pretty often.
Smart peeps - Good internet and computer security, checks their links, doesn't go to bad websites, cleanse their computers from time to time, etc. Often brags about how they don't need authenticators because they know how to be safe, until a more hidden or fancy keylogger gets them, as the goldsellers are in desperate need of a constant flow of gold to sell, and smart people usually have more of this, making them attractive prey. This group rarely gets compromised - but claiming they're as safe as those with an authenticator is a big, fat lie. Ways to get compromised: Bad ads on usually good sites, catching them unaware, attacks with new technology bypassing their computer security, etc.
Authenticator'd - Internet and computer security varies between the stupidasses and the I'm smart-groups. Many would be at high risk, many at low, but the authenticator, stopping all the low and semi-high threats, makes them all VERY RARELY COMPROMISED. Ways to compromise: Direct attack, man-in-the-middle, compromisers needs to log in on the account immediately after the one-time code has been written down.
You're all just a few dollars/pounds/euros/whatever currency eligible away from moving straight to the last group. A pretty good deal, if you ask me.