Meteor works a lot like Heroku, and that's the monetization strategy.

Currently you can push your Meteor apps to their servers and host/run them for free. But eventually they're going to charge, have add-on services, etc. Just like Heroku, but because these are the guys who built Meteor, it should be better.

It will be interesting to see if anyone else tries to host Meteor apps at all, Heroku/Salesforce should be watching closely.