They don't need much traffic to send tracking data, so they can get a cheap data plan for the planned life time of the device.
They can even add the costs to the price of the device.
Tesla cars report their state back to Tesla HQ and have done so for years, this is one of the things they were banking on for their self driving work - the ability to train their systems on millions of miles of actual driving data. I don't know who pays for that connection, but they made it work.
Around 2010 the Amazon Kindle 3G with keyboard had a cellular connection for buying books, and it also had an experimentat web browser with worldwide free internet access.
I don't know who pays but it already happens, it's not new to 5G.
They’ll use a mesh network to find a cheap path out. Amazon and Apple already have their own and it’s not going to be long before one starts leasing time.