As mentioned in the whitepaper:
Every day the reward pool is distributed among all post, according to the upvotes.
If you take a huge chunk, there is less for the others.
You are also taking a part of the reward pool that is in no proportion to the content you provide.

On steem, as there is no police, everyone has to decide for themselves, what's ok and what not.
In my humble opinion, the use of bidbots beyond a payout of 50 is not ok; also people notice this and take you less seriously.
The fairest way is to constantly provide good content, maybe invest 5-10 steem here and there for bidbots, be consistent and patient.
Greed's the biggest killer of all.

btw.: As you said, you pay for it. The profit goes to bidbots.

people also might frown upon self-upvoting comments.

and: A downvote is a very bad reply to serious critizism. I mean, I spend time here explaining steem to you.
Shows how new you are. I'd tread carefully.

Bid bots are a contract between you and the bot operator, they are not an inherent feature of this blockchain.  As @captainklaus said, if people feel you are being disproportionately rewarded, they can return some of those rewards to the reward pool.  It's your choice if you want to take that personally, but it's a bad idea, especially if those people are attempting to explain the mechanics to you.  

I find it strange that you are so new to STEEM and were able to bid bot your first post, but don't understand the wider implications.

as usually, the captain is right. Listen to him, instead of downvoing him, @ethsensei.