I have dealt with this problem before. Even if you are a first mover, you will still have indirect competitors, and customers used to paying a certain price and buying at a certain frequency. Talk to your customers, find out how they are consuming, and position your product accordingly.

Really Basic Example: A skype based cell phone should be priced similarly to comparable phones, with a premium because skype is cheaper than other cell phone plans.

For web products, one trick I learned is to use Google Adwords with different prices and features listed, and observe CTR.