This actually causes me to _not_ try out your service, even though I think I have a few customers who would benefit greatly.

With the cost unpredictable, we can't say if it will be worth it. Plus with no price, it makes it seems like this is just a hobby and you may decide you're bored with in a couple of weeks.

To attract paying, commercial customers: state a price, and then give a free 3 month trial, no cc required.