A few people answered correctly to my little challenge, but not everyone.
At first sight, the rules look pretty favorable to the player: half of the time, I lose my money, but the other half, I get back at least as much as I bet.
Or do I?
Well, no. If you look at the rules carefully, you realize that what you are getting back if the roll is over 50 is not as obvious as it looks. Take the 66-75 range: you get 1.5 times your money, but you need to remember that part of this is the original bet. So if you bet $1, rolling between 66 and 75 will only make you richer by $0.5 and not $1.5. And the same applies to the other rolls.
Your gain expectation therefore is:
-1*0.50 + 0.5*0.10 + 1*0.24 + 2*0.01 = -0.19
For every dollar you bet, you will lose 19 cents.
Here is a simulation in Ruby:
fortune = 0 max = 1000000 for i in 1..max do n = (rand * 100).round if (n < 50) then fortune = fortune - 1 elsif (n >= 50 && n <= 64) then fortune = fortune + 0 elsif (n >= 65 && n <= 75) then fortune = fortune + 0.5 elsif (n >= 76 && n <= 99) then fortune = fortune + 1 elsif (n == 100) then fortune = fortune + 2 else puts "#{i}: n:#{n}" end end puts fortune
and the output:
$ ruby ~/t/game.rb -184887.0
The mistake that a few commenters made (and which I made as well initially) was to have a few extra "ones" in their gain calculation.