Why are sellers all crazy?
If you mean used car dealers, they overcharge because they can finance people and talk in terms of payments rather than price.
But I think you meant private sellers, so I will let you know what I do. Often I find sellers that ask prices that are too high are not trying to cheat anyone, they just have attachments to their cars and don't realize how much they have lost value. These people often take better care of their cars and part of them doesn't really want to get rid of them. So, when I find a car that has been exceptionally well taken care of (but with a price way too high) I leave them my card and let them know if they are willing to come down on price to give me a call, and often a couple weeks later I get those calls.