Besides the unnecessary add-ons, a ridiculous “Dealership preparation fee” - ranging usually from $300 to $1,000 - is added to the invoice.
When you query this, the dealer tells you they etched the Vehicle Information Number on the glass (or peeled off the plastic protection of the car, or similar) for you. This is an effective way to prevent theft and is done by applying chemical etching of the vehicle's serial number to your car window, which makes the car parts basically worthless. However, etching is something that would cost you $20 if you did it yourself.
How to avoid: tell them in advance you do not want this done. When you sign the contract for the car, look at the small print very carefully. They can’t make you pay for something you didn’t order.