> It's a shame there aren't more affordable connectivity options for projects like this.

There's tons of options, and the "professional" grade routers aren't much more expensive than that consumer grade AC800s. With the one I have I get a removable SIM, dual SMA antenna connectors for MIMO with the ability to have an external high gain antenna, 5 ethernet ports, and a box that runs a version of ddWRT that I have full control over.

The AC800s is $200, my modem was $350.