I assume for the radio to stay on, it's either subsidized by the parent company (Amazon pays for Alexa's 5G) or I'm paying for a subscription (Xbox subscription pays for 5G on some future mobile XBox)

Maybe you could get the cost down to $1 / month. If you invest $400 in the market it should pay out about that much, so you could make it a one-time payment of $400 for a 5G chip.

Consumer network connections, of any kind I'm aware of, don't go down to $1 per month. Maybe with a big volume order and a low bandwidth cap the cell companies would do it, or maybe 5G itself is just cheaper, but where does that monthly cost come from?