Earlier quoted context omitted.
Exactly how profitable does a market need to be to require showing margins to the customer? Where are you drawing the threshold?
Who said anything about a requirement? It suffices to make it illegal to prohibit disclosing the fee. Businesses can decide if they want to do so. The point is that this 'invisible rake' model is being exploited to nullify free market forces in service of obscene profit. Many businesses (not just Apple and Google) have realized they can leverage this to make considerably more money than they otherwise might.
Sorry, between this line and not realizing you were also the GP commenter, I assumed you were suggesting the markets be forced to disclose the rake pro-actively themselves.
Making it illegal to prohibit disclosing the fee is great, and at that point I don't even think you need to make the case that the industry is different than others. It's not the same as the cost, but plenty of items have an msrp listed on their packaging. You know if your Arizona Iced Tea is being sold at a higher than usual mark-up because it's not $1.
(Disclosure: I live in San Francisco and have no idea whether Arizona is actually still a dollar in other places.)