It is not the payment of the TurboTax fees preventing you from filing by mail, it is the payment of your tax bill.  Go back through the File section in TurboTax.  When you come to the screen that asks how you want to pay your tax bill, choose a different method.  You do not have to pay through TurboTax.  You can choose Check or Money order and either write a check or use the IRS website to pay your tax bill.  IRS - Make a Payment

There are several different ways to pay your tax bill in TurboTax.

• Direct debit (free)
• Credit or debit card (convenience fee)
• Check or money order (free except for postage)
• IRS Installment Agreement ($120 fee or free, depending on circumstance)
• Cash (at a retail partner)

If you already filed your return with the IRS, choose a payment option through the IRS instead of trying to pay through TurboTax.