It's called having a loss leader, and there are hundreds of products/companies that do it. You commonly purchase products sold as a loss leader. Hell, steaks at most restaurants are sold at a loss with the hopes you'll order a drink.

In this hypothetical situation, Google uses its internet access as a loss leader to sell hypothetical services which require high speed broadband. Traditional ISPs will use internet access as a loss leader to other services, such as phone and television.