Last week I had a conversation with a founder about how much they should charge their first few customers. Cost plus a fee? Slightly below the incumbent? The same as the incumbent? Some fraction of the estimated ROI? My answer to this question is pretty simple: charge as much as you can get, charge whatever the market will bear.
At an early stage, a founder's time and focus is the firm's number one asset. Any compromises made in getting less than the absolute maximum amount that a client will pay creates an unrecoverable opportunity cost. Early-stage companies can't afford to not charge what the market will bear.
Pushing for the max more has other benefits. It helps to determine the product's real worth and the real challenges the client is having in buying the product. When pricing makes buying too easy you don't get a good sense of the challenges you'll encounter down the road, you don't get the real story. It also generates a level of respect from the client (we've all heard the stories of people appreciating things more because they cost more regardless of the true value).
Finally, often a startup's instinct will be to charge less because it'll move the deal along faster. This is a myth. The opposite is true. The larger the deal the more attention it will get, the more senior people will need to be involved and it'll move faster as a result.
This post isn't meant to say that you shouldn't negotiate, do a pilot and be flexible where and when it makes sense. You should do all of that. But in lieu of a defined market price, charge a simple one -- the absolute most that you can get.