All of my low-mileage classics (i.e. I barely drive them or they are in pieces) are insured with Hagerty. My daily and my high mile classic are insured with one of the big name carriers you know very well.
Yes to be fair you have to consider insurance like any other product. Hagerty is a company tailored to limited use cars that are exposed to much less risk. So hence they can offer lower price coverage due to less pay outs.
As for high miles drive. More exposure and risk and more pay outs so higher cost..
if you want a hamburger you go to Mc Donalds and if you want steak you go to the steak house. Both meat but two different products.