Well is it your fault you got sucker punched... NO, BUT it's a Universal truth, Nothing good is cheap, and if it sounds too good to be true? Then it is. Remember this, never forget it and you'll be good to go. The last little bit of consumer wisdom I will offer today? Never, ever ever, be impatient. Take your time, it puts you in the prime seat and will take away a huge chunk of a salesmans power when buying a car for instance. Remember that no matter what it is, (Unless it's a super rare collectable) there are hundreds more just down the road.
So, Be skeptical, be patient, don't trust anyone... Pisser you got worked though man...