how much is the fee when paying with a credit card?

Your fee is based on which version of the software you used.

How can I see my TurboTax  fees? 

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-account-billing/review-fees-turbotax-online/L1XnIzgzg_US_en_US?uid=m682vq7k

If your TurboTax fees are higher than expected, you can reduce them by removing add-ons     (BEFORE you e-file) :

• Remove Premium Services
• Remove MAX Defend & Restore
• Remove a state
• Remove PLUS Help & Support
• Remove Pay With Your Refund

There is not a fee to e-file your tax return or to have direct deposit of your refund.

Did you choose to pay for using TurboTax by having the fee taken out of your federal refund?  That means you will pay an EXTRA FEE of $40 ($45 in CA) to have a third party bank receive your refund from the IRS, take out enough to pay TT, and then send you the rest of the refund.  ( The third party bank keeps the $40 or $45 fee for itself.)

You do not have to do that.   Pay upfront BEFORE you file --- pay using a credit or debit card.

REMOVE REFUND PROCESSING FEE

https://ttlc.intuit.com/turbotax-support/en-us/help-article/intuit-account-billing/remove-pay-refund-fees-turbotax-online-change/L7UxC6ZZp_US_en_US?uid=m6r4xelq