are the 'Genuine Apple 60W MagSafe' Power Adapters on eBay actually genuine/safe to use?

hey guys,

I am thinking purchasing a back up charger because the one that i have doesn't have great connection with the laptop. The adapters on apple.com are $79 but on ebay these 'Genuine Apple 60W MagSafe' adapters are sold for only around $30. Are these actually the genuine adapters? Why are they so cheap? 😐

here is an example:

http://www.ebay.com/itm/Genuine-New-Original-Apple-60W-MagSafe-Power-Adapter-Cha rger-A1344-MacBook-Pro-/261652991490?pt=LH_DefaultDomain_0&hash=item3cebbbce02