It totally depends on where you are in the product life cycle. Of course you want to get paid but you also need success stories and objective information about your product and how to improve it, especially if it's a newer product. You could always limit the pilot to 60 days and charge for professional services up front and then get the subscription after the pilot if it goes well as an alternative. I think you need to evaluate long term value of the customer - will they be with you for 6 months or 10 years? What's the difference if you start off in a pilot without a large sum of money exchanged if the relationship lasts over multiple years and they generate referral business for you that exponentially increases. Have some other ideas that could be helpful if you want to chat through it.