You typically do not get charged twice for having Microsoft 365 on multiple devices. A single Microsoft 365 subscription allows you to install the apps on multiple devices, including laptops and mobile phones. The subscription fee is generally for the account, not per device. Therefore, you would not pay $159 for each device; instead, you would pay for the subscription as a whole, which covers all the devices you use it on, as long as you stay within the limits of your subscription plan.
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