I wonder what would happen if Facebook and the other megacorps currently objecting loudly to Apple's policies on this topic lobbied a government or two to legislate mandatory disclosure of this 'tax' at point of sale, as well as the restriction on mentioning app developers' other points of sale, overriding any contractual agreements or corporate policies to the contrary.
For example, requiring language like this on the final confirmation screen before completing each purchase:
"Legal notice: Apple will receive 30% of the price you pay to purchase this app or to make purchases within this app. Apple does not allow this app to mention or direct you to any other way of making purchases from this app's developer which does not involve paying Apple 30%."
(Naturally the law would be written not to be specific to Apple or to the 30% number, and a given app store's version of the notice could omit the parts which don't apply to that store's policies.)
For example, requiring language like this on the final confirmation screen before completing each purchase:
"Legal notice: Apple will receive 30% of the price you pay to purchase this app or to make purchases within this app. Apple does not allow this app to mention or direct you to any other way of making purchases from this app's developer which does not involve paying Apple 30%."
(Naturally the law would be written not to be specific to Apple or to the 30% number, and a given app store's version of the notice could omit the parts which don't apply to that store's policies.)