I used Heritage to buy coins in the past: they were coins that were auctioned. Some bids I won, some bids I lost. It was to say at least exciting to win a bid: but like gambling you have to stay within your budget.
Great Collections falls among my "core" of about a half dozen vendors and sources (almost all PNG affiliated) I've settled for daily/weekly perusing to keep up on possible want-list activity. OR just suspense research to see just how high something will go compared to Greysheet or TPG pricing. I've made one or two GC coin purchases. They are very upfront re bids and add-on buyer fees so you know going-in when you make that Click. I'm currently involved in two GC auctions closing later today...one I am determined to win