If you live in a jurisdiction where you need to pay sales tax, you will pay that sales tax, it will be on top of anything that the seller would normally charge you. You can't escape this tax by going to a different seller in your same jurisdiction. You can choose to move to a different jurisdiction if you don't like paying that tax, but a seller who sells in both will charge you the same subtotal (+ different tax).
Same with Apple's 30% fee - it's unavoidable on their platform so it acts as a private sales tax on their platform. Some developers might choose to essentially subsidize their apple users by charging them the same price on Apple and on tax-free platforms like the web. That may be out of fear for Apple or out of cultural inertia or whatever, but it doesn't make sense, they're the ones leaving money on the table, not the ones who charge people taking into account the cost of doing business with those people on their preferred platform. They could get more profit selling their app for cheaper when not subject to the 30% platform tax, if they think that their pricing with that tax is optimal.
Same with Apple's 30% fee - it's unavoidable on their platform so it acts as a private sales tax on their platform. Some developers might choose to essentially subsidize their apple users by charging them the same price on Apple and on tax-free platforms like the web. That may be out of fear for Apple or out of cultural inertia or whatever, but it doesn't make sense, they're the ones leaving money on the table, not the ones who charge people taking into account the cost of doing business with those people on their preferred platform. They could get more profit selling their app for cheaper when not subject to the 30% platform tax, if they think that their pricing with that tax is optimal.