In any case, even if the developer is only on the hook for the 70% of the sale price, Apple is the cause of people asking for refunds. As such, Apple should refund them their money. Afterall, it was Apple's approval process that failed if it allowed some of these products into the AppStore where they were sold for months before Apple 'realized' that they were in violation. (At least according to Apple's official word on the subject)