Well explained. Now I know how to define EV and +EV depending on how the prizes will be. Is it all depends on the house on how much the EV or +EV will be?
Yes, and you can actually use EV to determine house edge in most instances. Most traditional games in casinos end up being -EV, though there are times when certain sites have promotions where they lower edge to 0% (been a while since I've seen something of the sort). This is also why you shouldn't ever gamble more than you can reasonably afford to lose, because you're going to lose over time with almost all games.