Think of all they get, express and implied:
- software (of course!)
- a recommended deployment configuration
- an upgrade path they can accommodate (number of releases and upgrade procedures)
- all the benefits your sales guys tout: cost savings, improved operational efficiency, etc.
As you develop software, and as you define your processes for release, support, sales, etc., consider what this will do to your customer's overall experience. Your customer thinks of the entirety of his experience with your software; so should you.