What is the perfect medium to promote an over priced premium brand product?

If it is literally "Over Priced" then no one will buy it :) Premium products are made for class A+ customers, and those are very limited number and depends on the nature of the product; you can target them, for instance if we are talking about high profile financial investment service for instance "Over 10M$" you can target diamond and jewelry events, Yacht exhibitions, businessmen clubs, high value real-estate events.....
just think were your prospects are? what kind of activities they will be interested in; which has a similar premium products or services.