There are two main reasons that there is such a price difference.

In both cases this has absolutely nothing to do with the levels of service, customer support, backup or quality.

Instead when you buy a gap insurance policy from the dealership you bought the vehicle from the must quote you a price which includes IPT.( inurance premium tax) ( almost like vat on insurance policies).

When you buy from the dealership this price includes IPT charged at 20%.

When you buy directly from an independent source you are charged a lower rate.  So the first reason is not their fault at all.

The second reason for the difference is price well I will let you decide?

Another reason for the price difference is all about economies of scale. If you can imagine that the average dealership may sell 1000 vehicles per year. Now lets say that they sell the national average amount of gap insurance policies, that means that 1 in three customers buys a policy. That is 333 policies per year. The are online brokers who can sell that amount in a matter of weeks. Literally weeks. 

Also online brokers as far as I am aware or at least the ones I have spoken to do not have to pay commission to sales executives, business managers or sales managers. This too can affect the price.

Online brokers do not have to have plush dealerships instead the three I looked all had more modest business offices. Google street map – fantastic. Hey why not have a look yourself. No gardeners to pay for there! So by keeping their costs low they are able to pass a real vale for money price. In some cases the difference in price can be as much as 85% less than main dealership prices.

So why not have a look on line and let the only compromise be the price of your gap insurance policy.