Using an Apple Watch with its own cellular connectivity will cost you $10 per month if you're living in the United States. On top of the $399 base cost for the wearable, carriers in the US will charge the same $10 monthly service fee. Every carrier but Sprint has confirmed they'll provide three months for free.
Some other carrier-specific benefits have been announced. T-Mobile is waiving its $25 new SIM kit fee and neither AT&T nor Verizon will charge for activation.
The $10 fee associated with the Apple Watch Series 3 is higher than usual on Verizon, which normally charges $5 per month for wearables.