They mean essentially the same. As always in a language, there is an ever so slight change in connotation when you express it differently.
@"...want to sell": They have the plan and intention of selling, might have taken steps in the direction.
@"...willing to sell": They can be persuaded to sell it.
For example, if I want to sell my car, I might put in a sign saying so. But even if I didn't want to sell my car (had no prior intention of doing so), I might be willing to sell it when someone offers a good price. - I hope that makes sense.
"Wasn't it worth everything" - never heard it used like that. Though not wrong as such, it just sounds a little off, can't quite put my finger on it.
Hope that helps!