We weren't going that extreme, but were basically looking at switching from Platinum to Bronze but using an HRA, but yes there were significant savings. What was interesting about the entire process is that I interviewed between 4-5 brokers, and not a single one even brought the option of self-insuring as a possibility for us to consider. We ultimately went against it because I was worried about the service from our broker, as they were not enthusiastic about going the HRA route. (Lower base fees = lower commissions)
The HRA is a great way to self fund. I strongly endorse this approach. Id demand this of my broker.