Alpari list low payouts for binary options on their website, but show high payouts for demo accounts in their android app. I asked them about the difference, and they basically said that the demo version lets people test the concept, without limitations on the availability of different contract types. Real accounts limit the availability of certain contracts when liquidity is low.
So basically, I if I practice on a demo account and get good at it, then I can't expect to win as easily on a real account.
I use Binary.com who have assured me that their demo accounts work exactly like their real money accounts.