While I was doing the "free 30 days + 12 months of free stuff", a certain level of MSSQL was listed as free, but hidden under that is creating the storage for MSSQL which is a separate and additional cost that you cannot avoid. (At least, not that I could figure out.)
By the end of my 30 days, I found the bare minimum performing low volume .NET + SQL on Azure was going to be $30+/month even for just a prototype/development site, and I can pay less elsewhere for higher performance (though perhaps less control). And when I say "performing", I just mean the VM not being too slow to actually use as a UI, and throwing low memory errors constantly. The free tiers for Windows Server are, in my opinion, unusable at all.
I run a hobby .net core website on a $5 digital ocean instance and it runs fast as hell. You definitively don't need to spend $30. I'm using a PG database but it looks like maybe it would even be possible to run SQL server on a 2GB instance.
You do get some free storage with the free tier database, but it is only a paltry 32MB. Additional storage is only $0.221/GB/m though. The paid cheapest SQL database (B0) is only $5/m, which comes with 2GB of storage. In practise, this is absolutely fine for light usage.
By .NET + SQL, I assume you mean you were using an App Service? They come with a lot of convenience, but I definitely agree that they are too expensive, especially when considering the level of compute you get. I raised this with someone from Microsoft before, and they said they were confident the value offered was worth it.
There is a free tier for App Service though. It's a shared compute model - I tried it a while back, and the performance was totally fine for light usage.
I wouldn't try to run Windows Server on a B1S, as they only have 1GB of RAM :) You might just about get away with it for Server Nano, but I've never actually used it. Best stick with Linux or BSD for these tiny VMs.
By the end of my 30 days, I found the bare minimum performing low volume .NET + SQL on Azure was going to be $30+/month even for just a prototype/development site, and I can pay less elsewhere for higher performance (though perhaps less control). And when I say "performing", I just mean the VM not being too slow to actually use as a UI, and throwing low memory errors constantly. The free tiers for Windows Server are, in my opinion, unusable at all.