Sql Azure Pricing and questions

I am having trouble getting an estimate of monthly cost for a small SQL Azure database I will be creating.
When I use the pricing calculator it seems way out to lunch with the lowest option way more than I would expect.

The database is for cloud enabling a VB5 Point of sale type application which is installed at 40 store locations using an Access Database. ( I know- bad idea but that's what my client wants to pay me to do - 250,000 lines of code so no budget to rewrite it) I plan to create a sql azure database and use an API (PaaS) to allow all the locations to use common data.
Each location would only have a average of 100 DB calls to a single Members table for accessing Memberdata and Rewards Program data. There will likely be a small number of additional tables for reward data etc.

I expected this would be less than $25 / month but the calculator says much much more than that. That said, maybe SQL azure is overkill.
Also, I would appreciate any ideas for keeping the on prem Access databases in synch with the Azure data. I want to do that in case of loss of internet connection at a location.
I don't think I can use Azure SQL Synch because all databases would need to be SQL Server DB's I was thinking that when a member makes a first call to the API -> database, it would return the member data and if the status code is not 'unchanged', the member data would get written to the local Access DB. That would handle updating the local access db, but I am not sure how I can trigger an update of the other 39 on prem access db's Maybe use some kind of Azure Function?

Is there maybe an Azure agent that can be installed on the on prem machines that would allow Azure to send it notifications or events? Worst case- I could put a timed function in each vb5 app to check for member changes somehow.