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SWIFTCASH UPVOTE: 150% of the value you send us! (~12.50% profit after curation rewards)

But curation rewards can be as little as 8% for the curator! Pretty sure the ROI after curation rewards will be more than ~12.5% and it's impossible to get the exact number before then...

That's 12.5% profit in author rewards. People usually understand it this way because it's also how it's written in steembottracker.

But this is a curation bot and if people wanna make money, I would advise they buy swiftcash and stake or run a masternode than buy upvotes. And as I said above there is no way to calculate the exact number when it comes to curation rewards. Best way is to say how much upvote the author gets on his/her post. How much of that will go to curators and how much of it will go to the author is something that will be known after the post is finalized on the 7th day.

Author share can be calculated though...

Not sure about the author share but curator share can't be calculated, because it depends on the next curators and the last curator gets the least.

Author share is relatively easy to calculate. If I send 0.100 steem to your bot and it upvotes for an equivalent of 150% of that, then I'm getting an upvote worth 0.150 steem. 75% is the author share, which is ~0.112 steem.

My suggested text does not account for curation rewards and it explicits it is based on author share alone. We all know there wll be some curation rewards and that we don't know for sure how much it will be, so it's fine.

That's not really true. The author can get more than 75%. It depends on many factors like the penalty for curators within the first 30 minutes. I might change the description to something like this: Minimum ROI: +1%. Once the 150% ROI promotion period ends, I will change it to 126%. That way the ROI will be gauranteed to be a minimum of +1% and depending on how much curation rewards will go to the author, the ROI can increase up to 10% or even 15% or perhaps even more. And in the meantime, I will change the description to Minimum ROI: +25%.