I didn't mean to offend you Drawmer, but it is something that happens commonly. Assuming
you' are selling house insurance to someone, would you - personally - ask the customer 'what is the value of your house' or 'what would be the cost of rebuilding your house'? I suspect it is the former. In which case the client is paying over the odds for insurance - if the house was burnt to the ground, the insurance company would certainly not pay out the market value of the house! OK, maybe I used the word 'con' in a broad sense. I am sure the insurance companies keep within the law, but in terms of what the customer perceives they are paying for and what they are getting, I think it's a fair comment. And I am also sure that the insurance companies are well aware of this, but choose not to point it out to the customer.
Likewise, with car insurance, when filling forms, you are asked what the value of your car is. This has, a direct bearing on the cost of insurance. Most people would base the answer to this question on what they paid for the car. However, if your car is written off, you will be paid the lowest value possible (hypothetical auction prices?) - in many cases this would appear to be a theoretical value, and there have been no end of stories of people who are unable to buy an equivalent replacement car with the money paid out in an insurance claim - this isn't based on my own experiences, but on many articles in the press.
Incredulously, insurance companies even offer something called 'GAP Insurance' which is a separate policy to pay any shortfall if the insurance company fails to pay out enough to purchase an equivalent replacement vehicle (see ' Replacement GAP Insurance '
http://www.carinsuranceexplained.com/car-insurance-explained/car-gap-insurance.html) - even though the insurance ombudsman says they are not allowed to do this.