In the previous month. My website's active users per month increased from 5K to 15K.
Then my azure cost also increased a lot. The main cost is from Azure storage account and Mysql.
Then I moved my website source code from Azure file to Local files. It increased the performance and also reduced the cost.
The good thing of Azure file is that you can backup the files and recover easier. With local files, you have a risk of losing files. What I did to overcome this problem was that I created a git repository for my website code then pushed my files to bitBucket. And I also put the whole git repository into dropbox sync folder. It's a great solution for me. I found it even better than azure files, because I have better controls of the files. I can test my website locally, then push the changes to remote. Then I can pull my changes from VM. If bad things happen, I can checkout previous commit to recover.
My forum is still running using azure file. My next step is moving it to git as well.
Then I will think of using local files for mysql as well. Too conclude, expensive solutions is not always better than free solutions.