I'm still not sure how much a single customer is worth in terms of money. Our entire pricing model is based on inexpensive hosting (trying to talk intelligently without self-promoting...hard on this topic) so a single customer for one month isn't worth much. In order to answer that we'd have to know how long a given customer will stick with us and what upgrades (if any) they will purchase.
I honestly believe it will take at least a year or more of really good tracking for that 'average' number to become available. And then of course there is the issue of not all customers being 'average'.