The best published sale is shop.app, which sold for 200,000 usd. jackpot.app, jackpots.app and gambling.app are owned by large companies (other young extensions do not include .io). Casino apps are also the future, gambling companies are investing massively in casino apps. The .app extension is in the hands of Google and the extension is only three years old. I am not asking much for the domain. Registration costs are, by the way, 1800 usd a year.