I'm surprised that anybody can be disappointed by high availability. If you really want *low* availability, it won't be too hard to achieve. ;-) I'm not sure what your actual problem really is. The fact that high availability requires redundancy? That's nothing specific to Azure - you can see many companies having extra servers just in case something fails and they're replacing them every couple of years. Maybe you're comparing completely different systems in Azure and on-premise...
How much will cost you if you build, install, maintain and upgrade the same amount of servers by yourself? If you're fast growing, you'll have to either oversize your servers from beginning, or replacing them with new ones. And you'll never achieve the same level of flexibility.
As I already mentioned, paying for the same amount of load for 24/7 usually doesn't make sense with cloud-based solutions (unlike with on-premise servers). It doesn't seems to be included in your calculation, therefore it likely estimates buying more load then you really need.
This all being said, it's up to you to decide whether Azure makes sense for you or not. If so, use it. If not, don't. You won't change Azure pricing policy by complaining on Dynamics AX forum.
It seems to me that you mix two separate problems:
- that Azure looks expensive to you (I hope I brought some perspective to it)
- that you want to make a more precise infrastructure estimation (which would require more information from you or actual measurements, as mentioned before)