Blake-
To get more out of the effort, you may want to call them and ask if you can drop by with some business cards for them to pass around.
You can casually tell them that part of your strategy is to find a good customer with some challenging work, as you know from experience that good people that get good work done for a really good price are your "word of mouth advertisers". You could have bid more, but you were in effect, hopefully paying for advertising, thanks for supporting a locally owned business, and please tell your family, friends, co-workers. Even smoothly add in an anecdote about how you got 7 jobs from a customer putting up your business cards on their busy office bulletin board with their name along side the cards so the other office workers could get a reference.
No more outlay of expense, but maybe that simple suggestion will encourage them to sing your praises as a good businessman.