Okay, let's discuss the gory details
I suggest the following terms. Namely, if I become Legendary at 994 (my next activity value), you win and I owe you 0.001 BTC. If you still see me as a Hero member at any activity above 1,000 (i.e. 1008), then you lose and you owe me 0.001 BTC. If I turn into a Legendary member exactly at 1008 (980+14+14), that should be considered a draw, and no one owes anything to anyone. I'm not very familiar with betting mathematics, so you are free to change the bet size to compensate for the "house edge" if there is any
Let's try to keep it simple, then.
There's a 14/36 chance to hit Legendary at 994.
There's a 14/22 chance to hit Legendary at 1008.
This means the chance to
not hit Legendary at 1008 is 22/36 * 8/22 or 11/18*4/11 which is equal to 2/9. (22.222...%)
The chance to hit Legendary at 994 is 14/36, or 7/18 (38.888...%)
The chance to hit Legendary at 1008 is 22/36 * 14/22, or also 7/18 (38.888...%)
This all adds up to 14/18 + 4/18 = 1, obviously
Now for the betting amounts at 0% house edge:
Suppose we're talking in terms of mBTC, and n is our bet amount.
We will have the profit {
7/18*1 - hitting legendary at 994
7/18*0 - hitting legendary at 1008
-2/9*n - not hitting legendary at 1008
So, 7/18 - 2n/9 = 0 for 0% edge
Unfortunately for deisik, with these odds, this would be greatly in our favor, even if we were betting in a 1:1 ratio.
To make it fair:
7/18 = 2n/9
7 = 4n
n = 1.75
We would have to wager 1.75 mBTC for every 1 mBTC you wager to make it fair. Math!
(provided the math checks out, which I'm pretty sure it does)
But hey, if you want to gamble with a huge house edge, I'm down to be that house!