We wouldn’t drop our prices for an alternate store - we already know the user’s willingness to pay - we would either increase our margin or increase our ad spend at the same margin. The big winners here would be developers and Google/Facebook.
Ok and where is that ad spend going to direct people to go? To the store with the 30% tax or the store with the 5% tax?
You say you wouldn't drop your prices because you know what people are willing to pay as a counter argument to saying that lowering prices would incentivize people to shop at other stores while also stating that selling at other stores would increase your margin. Well, sounds like if you want to get that bigger margin, you should lower your prices to attract people to the lower tax store.