Yes, you are exactly correct. I generally assume the bigger bots will net a small loss, but I really don't mind if I think in the end I'll get enough total votes from other users to make it a great investment.
I've upvoted you, please consider resteeming this if you think it is worthy!
That's generally the mindset I take as well. It's also a possibility that the ROI turns positive if Steem/SBD is trending higher. Like now. Though 7 days is an eternity in crypto.
You got the math down pat!
7 days, even 7 hours, :)