Hiring those armoured vans to move it around, loss by theft or error by staff, time spent counting money, making cash deposits or withdrawals from the bank, and perhaps higher insurance.
Whether those costs are more or less than cash presumably varies. A public transport operator seems the obvious case where cash costs are high.
The EU capped fees at 0.2% for debit card transactions, and 0.3% for credit cards. I'd guess that makes them very competitive with cash -- the discount German supermarkets, well-known previously for only accepting cash, started to take cards. It also led to the demise of cashback credit cards, but I'm not sorry to see them go.
In the last 3-4 years, I've been surprised a few times when small businesses (plumber, street food seller, dry cleaner) have preferred a card.
[1] http://ec.europa.eu/competition/sectors/financial_services/d...
The store passes the cost right back to you, the consumer, in the form of higher prices. You didn't just think they absorbed the cost out of the goodness of their hearts, did you?
You can negotiate price with cash.
The payment card industry is a parasite on all of us, full stop.