The sober deposit is an amount of money that is paid, put aside and returned to you when you leave the house on good terms. You forfeit this money should you relapse or be asked to leave for any other reason. This deposit is set in place to motivate you financially to follow the house structure.
Why is it so much?
In short, because we have nice things. When an applicant wants into the house we do not consider criminal history (other than sex offenders) into consideration. We don’t run credit checks. We don’t do rental history checks. This leaves us vulnerable when we have a $1,000 Tv in a bedroom or a $4,000 pool table, etc. This deposit (although it doesn’t carry the full amount) helps us protect our financial investment in the house.