There is no fixed ROI you will get. BDD is a zero sum game (minus the fees). That fact that you started calculating a ROI means you will have to re-read the OP.
All this reaction from you over my stating what B.EXCH returned over the past 30 days. Must be completely utter news to you as you've never done spreadsheets on anything before. HINT: Openoffice plus high school math skills.
If B.EXCH lost 50% of your btc over a month, would you "play the game?" Course not.
If B.EXCH returned 8% profit over the last month, would you "play the game?" Maybe yes.
Just settle down. Sounds like 20's is your guru or bosom buddy of yours.
So what.
There is no fixed ROI you will get.
But you do get a ROI, else why play? Again, this deluge from you is because I did some work and showed that B.EXCH returned 8% for the last 30 days. What is so wrong with my stating that?
BDD is a zero sum game (minus the fees).
The NYSE is a zero sum game too. Again, what exactly is your point? That no one is really making money off B.EXCH ? I doubt that...
I don't think you understand the game.
1BTC goes in, and exactly (almost) 0.98btc is given as dividends.
If you hold on to b.exch (b.sell+b.mine) you are guaranteed a 2% loss (or whatever the fees are)
To put it simply, B.exch = b.mine daily div x 200. B.sell dividends = excess btc when difficulty increases lowering the amount of btc required to pay 200 days worth of b.mine divs.
BTW as anyone who has been mining for more than a week knows spreadsheets and calculations are just about as accurate as palm readings and fortune cookies.
But if you don't believe me then I'd encourage you to read/fully understand the rules and play the game as there is huge money to be made by anyone who can predict the future.