Really? I was recently looking for business accounts at the big 4, and I saw that after a minimum number free transactions, any transaction has a fee (cash or not).
If you accept cash -> banks have a fixed transaction fee (anywhere between $2 to $25 for any amount of money).
If you accept credit/debit/mobile -> there are atleast 2 transaction fees - one by the payment provider (generally % based) and one by your bank (fixed fee).
Cash has four transaction fees:
1) cost of storing it and counting it
2) cost of physically moving it to the bank
3) transaction fee.
4) increased risk of doing all of the the above.