If you could slowly dial up the ads while retaining most of the users, probably a decent amount as a small business. However, this approach has been tried and failed repeatedly. Strangely, open source folks often see this stuff coming and scatter / relocate before the 'profit' stage is ever reached.
The part that leaves me perplexed the most is that said lunch is two crackers with cream cheese.
How much money could there be in running an IRC network?