The price you pay for the TurboTax App/TurboTax Online is based on what you enter on your tax return. If you choose add-ons like Assist & Review or the Premium Pack (Audit Defence) then the price of those services will also be added onto your return.
Also, if you prepare your returns together with a spouse/partner, then both people will be using the same version of TurboTax, and so you’ll be charged the same amount for both returns.
Please see this TurboTax Canada FAQ for more information on who can use Free: Who can file for free using TurboTax?