What about OpenStack? OpenStack seems like the best of both worlds with being able to manage both your own hardware as well as burst to your OpenStack host's resources on demand. There are multiple OpenStack providers like Rackspace, HP, and many more. This means that if you don't like one provider, you can easily move to another OpenStack provider without being locked into 15 different AWS services. You may need to schlep your physical servers to a different datacenter, but that is still easier than decoupling your service from AWS.
From experience, I have seem that the price of performance on AWS is much higher than companies that buy their own hardware. Knowing what resources your service needs as a baseline can be helpful when picking which machines should be reserved instances, but still you may as well just buy your own hardware if you want the best perfomance/price.
From experience, I have seem that the price of performance on AWS is much higher than companies that buy their own hardware. Knowing what resources your service needs as a baseline can be helpful when picking which machines should be reserved instances, but still you may as well just buy your own hardware if you want the best perfomance/price.