Opening a channel (and correct me if I am wrong), you assign the satoshis in the channel point output of the funding transaction to three balances living on the channel by agreeing to them on a commit transactions between the parties:
- Your local balance
- Remote balance
- Reservation for a final commit fee
Essentially you create and share with your peer -but not broadcast to the Bitcoin network yet- a transaction that outputs:
- Your local balance to your Bitcoin address
- Remote balance to the peers Bitcoin address
- Leaves the commit fee for the miners
So, essentially when you open a Lightning channel you are:
- Paying a tx fee to open the channel
- Part of your funding is reserved for closing and never gets shows on your channel balance
The final commit fee is coming out of your pocket as the initiator of the channel.
So it could be said that opening a channel costs you two transaction fees. So you should make at least one payment on the channel before you break even (minus ln fees so you might need two essentially)
After that besides ln fees it's all gravy from there on with every payment you make.