I am starting developing new online business and I am not sure what technology to use for hosting. I have used Microsoft Azure in my pervious projects, I did not have any problem with it, it was just expensive.
My choices are Azure, Appharbor or Amazon EC2. I am not even sure if comparing them is right.
I am looking for something which is really easy to setup and takes less time.
We are only two developers so we just have enough time for developing our website.
I have heard EC2 will be time consuming.
AppHarbor will definitely get the job done.
Azure is also a PaaS (with lots of infrastructure features), but there's no add-on program so you're stuck with whatever services Microsoft decides to offer (or you have to install, configure and maintain them on your own VM-role instances). And as you mention, Azure gets expensive quickly.
AWS Elastic Beanstalk also has .NET support now, giving it some PaaS-features. The deployment-model is not very sophisticated though (and neither is Azure's): You have to have a Visual Studio plugin create packages that are then pushed and deployed whereas AppHarbor integrates with GitHub, Bitbucket, Codeplex, etc., runs your unit tests, sends build notifications and lots more.
(Full disclosure: I'm co-founder of AppHarbor)