You are right and wrong. Not many people go to that page. My home page is http://chandoo.org/wp/ where most of my readers and search audience end up. And I open Excel School once every three months. I am doing this as it gives me opportunity to spend time with students and learn / teach better.
You would see lot more links and publicity the next time it opens.
I will also be editing the home page HTML to add link ES and other product pages. Thanks for your suggestion.
Google docs, zoho and office web apps provide most of Excel's basic functionality. I am sure they will evolve to be more usable, functional during next 5 years.
And yes, you are right. 100k is revenues. Costs are there. Mainly rent, affiliate commissions, blog hosting expenses, site maintenance, outsourcing fees (to contractors). While I do not have audited figures yet, the expenses should be less than 20% of revenues. May be even less.
For a detailed breakup - see here: http://startupdesi.com/costs-of-running-web-business/
I did not include my hours in to this. But then I never do it.