That is correct. You pay the taxes on the price of the phone you’re getting at the time of purchas /upgrade. Depending on your carrier or promo going on, you can expect to pay anywhere from 32-51$ a month depending on the configuration of the phone you select. Typically your first bill will also have an upgrade fee, again, depending on the carrier you have.
You can also purchase the device outright and not pay an increased Monthly bill
Hope this helps.