There can be 175+ different territories that you may sell an app in, each with a different local price point. You also can't expect to simply show a converted $US dollar amount either as you may want to do price discrimination (so that the app is cheaper for regions that cannot afford the exact $US equivalent).
Overall options seem to be:
1. Don't show pricing and leave it for the App Store to display - the most common approach
2. Only show $US pricing on the website and let non-US customers manually translate to their local pricing - not a great experience for non-US users
3. Manually or automatically sync pricing on the website display with the actual current App Store pricing. This is quite a labour or integration intensive task and I've only seen this been done by large vendors