To use your car example, if the second-hand dealership tells you that the car you're going to buy has a 3L engine, but the manufacturer claims it to be 2L, who's at fault?
You always blame the first point of contact, the person who sold you the product, but most eTailers screw things up from time to time, and they will do their upmost to sell their goods, they sell things on their headline specs.
Another example
This would be as ridiculous as a car manufacturer saying:
"Ford Whizzbang 6-seat car 0-60 mph in 6 seconds"
Your going to think f*cking great, I can take the kids on holiday camping and show off to the girls behind my wifes back.
You buy it and then find out that it takes 20 seconds to get to 60mph, you then read all of their literature before you discover that its the 2-seater Whizzbang that goes that fast, you can show off - but your kids wont fit in.
You didnt buy a whole family of Whizzbangs you bought the "6-seater that says 0-60 mph in 6 seconds".
Most end users dont read all of the information, some dont read any at all. What people will read is the small amount of sales literature in front of them, and you are quite right the average person will always believe what they want to believe, and thats going to be whatever is in their best interests.
And again I will quote, this time from NewEgg:
"Western Digital Caviar GP WD10EACS 1TB 5400 to 7200 RPM 16MB Cache SATA 3.0Gb/s Hard Drive - OEM
New green power drive, low power"
They see this 1TB drive described as 5400 to 7200 RPM. This doesnt state that the reference to the speed covers the entire family of drives. They only see 1TB, 5400 to 7200 rpm 16MB Cache.
Their advertising is misleading, it doesnt matter how much info they put out if their headline specs are wrong, its headline specs people buy on.
6 seats 0-60 in 6 seconds
1GB 5400 to 7200 rpm
Andy