> You need to pay to send the GPS data to the satellite.
No, the device is only receiving the position data from satellites. It then sends the position via the network (internet) to you.
The phone will need network (internet) connection so you require a SIM card. GPS tracking devices usually use special data plans where the providers only allows a couple of megabyte per day, and thus cheaper than any phone plans.
https://www.eiotclub.com/products/gps-tracker-data-plans is $2.20 USD/month.
https://lightbug.io/product/lb-dev-ze2/ for example is 2-3.50 Euro/month if sending every 30 minutes is enough. The company probably pays less than 1 Euro for their data plan before they resell it to end users.