I'm recharging my Skype account with my Paypal account connected to my bank
How much are the costs ? I was wondering if I'm losing a lot of money by letting paypal get money from my bank account and send to skype
The costs are absolutely nothing.
By allowing PayPal to use your bank account, you are saving PayPal money - they don't have to pay your credit card company a transaction fee. That is the preferred mode of PayPal nowadays and they are doing their best to motivate people to finance their PayPal accounts with their bank accounts.
From my point of view, I'd rather use my CC and have another entity I can appeal to between PayPal and my money. But again, this means PayPal's cut from each of my transactions is lower (not that I care about it).