Why do I have to pay $220 for our combined tax return when my wife is the only one who is self-employed?

Unfortunately, because you are doing a joint return under TurboTax Assist & Review Self-Employed you will be charged $110 for each return. However, if you do not use the Assist & Review on your return then you can ask for a refund of the difference. 

Thank you for choosing TurboTax.