Insuring a car for competitions and track days comes at a price, and it’s expensive. It goes up in price depending on the type of activity your taking part in. For example, if you take part in drag racing a couple times of year, the price for your insurance will be very different from someone taking part in a single track day.
You may also have to take out more that one policy - one for track days, an off-track policy when your car is in storage, and another for the vehicle as well as personal accident cover which is particularly important if you take part in races.
The bottom line is that car racing and specialised car events is an expensive hobby and will mean you’ll pay premium insurance prices.