I never got charged more for OA than the published rental rates...but all the places where I did my checkouts had me fill out one extra sheet of paper so that an OA checkout also counted as a checkout for their own insurance rules. So if I was flying with a place a lot, I'd just do the checkout there and buy block time from them and rent under their non-OA policy. Basically, OA was great for everywhere other than one's local FBO, for which it was still typically a better deal to just rent under the terms of their standard non-OA policy.
Renter's insurance would be a tough sell for a lot of people; my local FBO already required it so I was good to go. (My local FBO is great, but they're also the only place I know that does dry rentals where you're not insured by their policy...weird, I know)
I'm not seeing any common sense in the founders.
1. For most people, doing an extra checkout is a deal breaker.
2. Same with the 10% (or more) additional cost. I wonder if that disqualifies block time discounts as well.
3. Also requiring renters insurance, which although recommended, most people don't have.
However, if you already lived near an OA location, and you squint hard, it could make sense for a handful of pilots - just not enough to ever make a profitable business.
There's an article about Blackbird linked to this article. They were trying to do the "hold out" Part 135 charters but regulated under Part 91 thing that the FAA never allows, and never will.