I just tried to visit PrimeDice.com but was redirected to a twitter page.
On that twitter page I saw that the jackpot is still being advertised as "roll 77.77 and ALWAYS receive 10x your bet!" (emphasis not mine).
But if I bet 1 BTC at 20% and roll 77.77 what do I receive? I receive 9 BTC, for a profit of 8 BTC.
10x my bet would be 10 BTC. Not 8 or 9. So in what sense am I receiving 10x my bet?
You receive 10x your bet. Meaning 9x your bet profit on top of whatever bet you made. So on a 2x multiplier you either profit 10x your bet or 8x your bet. Hope this makes sense.
I don't think it does. In the example I gave (1 BTC at 20%) my bet profit is negative: -1 BTC. 9x my bet profit would be -9 BTC. And how can "You receive 10x your bet" mean "9x your bet profit"?
The ad on twitter is misleading at best.