Developers won't actually absorb the full discount. A decrease in the fee will force a drop in prices (if that's possible) as developers attempt to find new customers with their newfound margin. If you have a more price-elastic customer base, those customers will reap most of the value of the shift as many will come to enjoy their lower prices.
Secondly, wouldn't this create the perverse incentive for developers of multiple apps to release apps under multiple accounts--some might call them shell accounts--in order to minimize their app taxes?
Mind explaining your perspective on why a decrease in this fee will result in a 1-to-1 drop in prices?
As far as point two, given that Apple is the 'benevolent dictator' of this app store, releasing apps under multiple accounts is a risky venture since developers and companies run the risk of getting banned completely. The overheard of wasting the time to actually do that also has to be small enough to make the potential gain worth while. Apps also seem to benefit from network effects, so it could hurt developers to spread their popularity for the same app across different apps in a discreet enough way that Apple wouldn't notice.
Secondly, wouldn't this create the perverse incentive for developers of multiple apps to release apps under multiple accounts--some might call them shell accounts--in order to minimize their app taxes?