1. Your total costs + some profit $ = Product Price
2. Your comparable competitors price + or - some amount = Product Price
3. A BullShit price you pull out of your ass that you tell people to pay or fuck off = Product Price
Explanations -
3. Apple is a prime example of this pricing model. nuff said.
2. Comparable competitor being the key phrase. I also suggest pricing higher and building a better product. Undercutting can start a nasty pricing war that can cause a lot of unndeeded revenue lost, on both sides.
1. This seems most appropriate for you. You can't just price at what you think the market says they are willing to pay. They may say they are only willing to pay $1/month. That's not going to cover your labor costs unless you have a ton of users. Figure out your labor costs associated w/ maintenance and additional features (don't forget to account for future hires). Price at that amount plus some profit (something like 10% or 20% if you have high labor costs. Don't be afraid to stretch that percentage higher too.) If you can't find a price point that covers your costs, but is in a range that users are willing to pay for, than you don't have a business.
Entrepreneurs often forget that you can build this kickass product that every user needs, but if the customer doesn't have a high enough ROI they won't buy the product.
User != Customer