Some example sentences from here:
Buying bulk will help you defray costs significantly by driving the cost down to what conventional flour usually costs.
Buying in bulk is just a discount, so no payment.
Many energy companies are now offering lease programs to defray the start-up costs and bill you on a monthly basis with a cost similar to your current power bills.
Renting something instead of buying it is also not a payment.
This does not quite defray the interest on the cost of their construction and equipment, inasmuch as it barely comes to 31% thereon, but rates and fares are deliberately kept low to encourage settlement and communication.
Keeping rates and fares low in the first place is also not a payment.
Discussing the rules and positive aspects of social networking with your friends and family can also defray negative repercussions.
Much like the OP’s example, this is completely unrelated to money.
I’m not sure where these examples came from originally. Some might be considered an error (especially the last). But I’m sure I’ve seen fairly common usage of defray as a general reduction of costs, not necessarily by actual payment.