i guess the house gets about 20 percent but id like too know why it seems they must make a killing at these sites is this the same at casinos also
Yes and no.
"Standard" rake online is actually more like 10%. The reason it seems inflated based on these figures is that a lot of sites bump it up for the very lowest stakes. Full Tilt charges 25% on a $1 SnG, for example. Play a $10 game, however, and you should only be paying $1 in rake.
Live casinos work on pretty much the same basis. Tournaments will include an entry fee, depending on the casino these can be pretty high and they're typically higher than online*. From memory, casino tournaments I've played in here (Melbourne Australia) have charged $50+$15, $200+$30, $150+$25. So 15-30% and again, they charge more at lower stakes.
Cash games work by either:
1 - Charging time (everyone pays a certain amount per hour to play in the game - some places just take it on the hour, others use a "collection pot" system, as seen on
Live at the Bike)
2 - Raking the pot, same as online
Of course, some places do both. My local casino charges $5/hr at $2/$3NL
and rakes the pot.
* Makes some sort of sense, I guess - online sites don't need to pay anywhere near as much in rent and staff, nor do they need to buy actual cards, tables or chips.