I am sure you come across many products advertised at mfg cost, vehicle's just happened to be a major player with this type of advertising, but buying used ?, to me that becomes what someone is asking and what someone figure it's worth, and that comes with study.

RE, buying a used car is like buying a mattress, yer thats true when buying a used mattress I am sure you will bounce on it to make sure the springs perform to your expectations, lol, it's like test driving a car and knowing how it's supposed to feel becomes the main issue.

RE, comparing apples to apples, yes, dealers in your area may have the same type vehicle and mileage for sale being but a few hundered dollars apart, it's now a question of how knowledgeable you become to seperate the two, you may even encounter same type vehicle asking price being a few thousand less, hmmm, I wonder why ?

Tell me something,,, when you go shopping for shoes or designer jeans, do you think asking for invoice cost is fair game ?

Yikes. That crack about shoes and designer jeans! I'm done.