Since they are charged a percent upstream, then they will have to pass that on to operate. So I would imagine they could pass on the percent component of cost

Since they are charged a percent upstream, then they will have to pass that on to operate. So I would imagine they could pass on the percent component of cost with no markup, and then charge a flat fee (ex: $1). I'm assuming they are never stuck with the bill in a fraud case. If they are, then the price should include that risk component as a percentage as well.