Providing support for your product is one of the keystones of building your ISV

Closes Sales by Clarifying Product Issues and Selling Your Company
Providing free tech support during the initial 30 day trial period by clarifying minor confusions about your product, but its also a time to introduce yourself, as a company, or at least a person within a company, in whom they can trust.

Invaluable Feedback
You can either program in the dark, trusting your gut as to what the world needs, or thinks about your products, or you can pay for expensive (read, practically useless) surveys, or you can turn the cost of tech support to your advantage by using it to listen to your customers to know what they they need, how they feel your product is answering their needs, and what they think of your pricing choices. 
This feedback, if done live (over the phone, remote assistance, etc) is much more valuable than any survey because its targetted to actual users, or at least potential buyers.
Their feedback, if you carefully listen, should give you a clear understanding of what is not clear to end users, what to add, what to remove, and how to price it.  All this can be gleamed while chatting away while remote assisting. 
Not a bad way to turn an expense into an asset, no?