I guess you are asking because of your trial with DuckDice.io
Bookmakers and Casinos often are using another definition. Like for example Nitrogen and almost all other affiliate programs:
"Every time someone you referred to Nitrogen places a bet you’re paid 0.3% of their total wager. A wager is calculated as the lesser of the amount bet or the amount that can be won on a bet. Whether your referral players win or lose, you get paid! "
This mean if user bet 100BTC on 1.1 at Nitros, you will get commission on 10BTC wagered, not 100BTC. There is longer explanation, but risk amount is what is counter in general.
Interesting, I wasn't aware of anyone that did this.
Is it because their house edge is variable? (i.e. if i bet 1 bitcoin @ 2x, or 1 bitcoin @ 1.1x does the house have a higher expected earnings on the 2x bet?) Or is it just an easy way to pay less money to affiliates?
Because for instance, on casinos with flat house edges (e.g. dice sites) it's a
lot better for the casino if there's low-risk bets
It is just an easy way to pay less money to affiliates. These are just Promotional thing which attracts at the beginning but pushes against when we get to know about terms
Same goes for some other popular sportsbook like CloudBet
While wagering rules in CloudBet is even worse. Wagered amount = stake (in mBTC) x price score (up to 1)
The price score is the square root of the odds, minus one (decimal odds). The maximum price score is 1.
Edit : But they all are clearly explained and not kept hidden