This question may seem silly. But most of the games even don't sell enough to pay back money that companies spend to make them.and how many times companies can borrow money from bank?after one or two failures they will bust.

The larger companies produce so many games and have such a large infrastructure, that they can afford to absorb the costs if a particular game doesn't do well; from the profits their more successful titles make.

Smaller developers do what independent film studios, recording artists etc. do - use bank loans, external investors...

They have actuaries estimate sales and develop a budget from there. If they expect to make $30M they would probably budget $20M for the game's development,

same way that films work - you find someone willing to provide the capital to create. EA are fairly self sufficient these days, but a smaller company would have to find a bank or people to provide the money.

There is a house edge built into the games.