Everything we offer right now is free. We do limit each user to 5 active recipes (although that limit can be raised for early adopters who want more), and we only check those recipes every 1-2 hours.
Our plan is to charge, at some point, for access to new, premium features: more active recipes, near-real time checking, other notification channels (sms, etc.),... Probably a few bucks per month, with a month or two free if paid annually. But none of that is set in stone.