It's not just about picking the winning team, it's all about how much money is on each side of the game. See the following example:
Team A - $50,000 total amount wagered on this team by all users
Team B - $25,000 total amount wagered on this team by all users
If you bet $1 on Team A and they win, you will win 50 cents (Team B Total wagers/Team A Total Wagers) + receive your original $1 bet back.
If you bet $1 on Team B and they win, you will win $2 (Team A Total wagers/Team B Total Wagers) + receive your original $1 bet back.
Team A - $50,000 total amount wagered on this team by all users
Team B - $25,000 total amount wagered on this team by all users
If you bet $1 on Team A and they win, you will win 50 cents (Team B Total wagers/Team A Total Wagers) + receive your original $1 bet back.
If you bet $1 on Team B and they win, you will win $2 (Team A Total wagers/Team B Total Wagers) + receive your original $1 bet back.