"Hosting costs" means electricity only.

You pay for the electricity your mining contract uses, nothing else. There are no extra running costs or hidden maintenance costs. The price depends on the electricity requirements of your mining contract. 

We calculate your hosting costs daily. So you only pay for the exact % of the hash rate you receive. When you check your balance history, you see a record of the amount deducted each day. These costs are deducted from your balance in Euros, so it is important to keep your balance topped up. You can do this with SEPA, BTCPay or credit card.