A puzzle full of chestnuts

The situation:

Monty gives you an envelope which has $100 in it. If you switch ties with Monty he will produce two more envelopes and open one of them, showing you a picture of a goat. If you don’t switch ties he will produce twelve balls. Eleven of them are made out of feathers and weight a pound each. One is made out of gold and weighs a pound.

Question:

Who got the extra dollar and who paid for the beer?