Her is a topic describing data amounts. Data use by Tempest + AIR station
And it is possible to run a raspberry pi with a usb dongle wifi hotspot and was mentioned in the archivesw thread to create a self contained system. I dont know if that would be any better than what you are doing already.
I have been considering similar ideas and also considering some logic to reduce the data amounts and then considering using LoraWan and The Things Network as free data comunications. But only in my ideas bucket at this stage.
And I have been enquiring about the fully remote systems which are unavailable to order for Australia and 6 months or more away from testing for USA.
Cheers Ian 