It's easy to enter the market and offer a cheap product. It's hard to enter the market and offer a very solid product. It's nearly impossible to enter the market and provide the hundreds of services the big players can provide, and operate at the scale they can provide, servicing the number of markets and customers they do, with the level of support they do.

The big players know that what separates the majors from the minors is trust. If you buy from AWS, you know what you get works, and you will pay a premium for that assurance. And also it is really fricking expensive to be AWS.