Thanks :-)
Yes there is gain, the gain increase as you rank increases and the rank increases when you receive more valuable votes from the Steemians. I'm saying valuable votes because it's not the number of votes that counts but how many SP the voter owns, that is his real SP not the one from delegations received.

This is the complete witness list: https://steemian.info/witnesses
Witnesses from #1 to #2 are currently earning about $1549 USD a week, so the gain is real here.
I'm currently ranked #113 and earning only around $15.10 USD a week.

So as you can see, I still have a long way to go in order to really saying that doing Witness is profitable to me. The only way for me to climb up is to get much more votes or a few more vote of higher values.

Witnesses need more visibility so they have to be more social and do more things for people to notice them. But new witnesses like me are competing in an unfair manner because if you go to the official witness list here: https://steemit.com/~witnesses you will not see my name in that list because that list only shows the first 100 witnesses. Worse, it even includes the witnesses that are disabled so we are competing not only against active but also against inactive witnesses.