If you take this attitude you should write all of your own tools, make your own hardware, not use any libraries (I might actually be able to make a case for this one).

I am most familiar with AWS, so all I can say is their prices have gone down over times, the availability has gone up, and the total number of services is amazing.

With other cloud vendors I think you might be at more risk of them shutting down services, but if they start doing that with out giving you multi-year notice it means they are going out of business.