This is why cloud providers build in as much lock in as possible in the form of managed services - eventually they won't want to decrease prices every year and you'll have so much code written against their proprietary cloud widgets that it'll be more expensive to move than to pay their increases.

If you ever take a vendor specific certification, it's all about how you should use their specific cloud features in order to "properly" architect the solution for the cloud. Often these services do in fact result in cheaper bills, but there are other costs - and no provider I've seen has ever made any commitment regarding future prices like you mention expecting.