In the case of my (free and completely standard) account that’s exactly zero Euro for every wire transfer. (You cannot transfer more than €50,000 and, as I already said, only Euro.)
Wire transfers are a very common way to pay for stuff in Germany and it’s very easy to get accounts that have free wire transfers. I would even speculate that most banks offer free wire transfers (I would at least be surprised if a bank told me that I have to pay for wire transfers) but I can’t be sure about that.
You are not using wire transfer companies in Germany, you just tell your bank the amount, name, account number (IBAN if it’s going outside of Germany), bank name and number (SWIFT-BIC if it’s going outside of Germany) and purpose of the wire transfer and you are all set.