Unfortunately phony cashiers checks are nothing new.  This has been happening ever since people got sketchy about personal checks.  Money orders are faked all the time too, so I'd steer clear of those as well.  This is one of the reasons eBay made PayPal a requirement for transactions.  With a sale of this dollar value I would consult with my bank as to the most secure way to be paid.  New scams appear all the time, and formerly safe methods become unsafe. 

Also, should go without saying, but never meet anyone you don't know alone in a location you don't know.  Even meeting people at your house or place of business I'd highly suggest being armed.  Some of the stories I've heard about people being assaulted due to fake Craigslist ads, etc. are quite frightening.