I’m modestly familiar with the principles at stake since I run a two-sided Australian marketplace. Essentially it is unlawful to display a price that excludes

I’m modestly familiar with the principles at stake since I run a two-sided Australian marketplace. Essentially it is unlawful to display a price that excludes hidden mandatory extras or is otherwise greater than the actual price a consumer will pay, and also unlawful to surcharge for card transactions above either your blended cost of doing so or actual cost on a per-transaction basis (the controls are scoped particularly to Visa and Mastercard, Amex has a bit more latitude). The ACCC loves prosecuting these cases and has scored many judgments against major brands on that basis. However, there is no requirement to itemise your price components, including those that are effectively surcharges for a given channel (as opposed to card scheme), nor is it illegal to simply be expensive, or to have market power, so Apple may well within those rules believe it can coerce merchants on its platform. The wheels are more likely to come off in other areas of the ACL, particularly those related to misuse of market power, unfair contract terms, and unconscionable conduct intended to mislead the consumer or distort a marketplace. These are rather more subjective and harder to prosecute since no absolute test applies; if anything it is Apple’s sheer scale and documented arrogance that might bring them into play.