"It will be good experience! And I'll give you a testimony to get your name out there."
As a professional in whatever field you work, have you ever heard this? Asking to have services rendered for free in exchange for a testimony and experience-building opportunity? I'm going to guess no, as asking an electrician to spend a few hours working on something for free, just seems ridiculous. How would you even go about asking this politely?
And moreover, you shouldn't.
But guess what, there seems to be a field of work that is the punchline to this joke, and it's literally no joke. Apparently, being a graphic designer means that you like to work for free, dislike money, and can live off the land and its many resources left on this earth.
It has become a sad, comical truth in the lives of fellow designers. I've seen a designer post an ad to Craigslist asking for free plumbing, because, hey, Craigslist-ers are asking for free design help. Eye for an eye?
When you're in college, doing free work to build a portfolio would be similar to an unpaid internship for anyone else. But once you're out of college, we don't need anymore free portfolio-building opportunities, but thanks for the thought.
As a professional, I do have the right to turn you down. Even inquiring shows a lack of respect for my work, despite the vehement need and glamor for it. Just because you compliment my work, doesn't mean it's free.
i.e. "Why yes, Doctor! These new implants are spectacular! I'll be sure to let all my Facebook friends know to come to you. And I owe you a drink!"
See what I mean?
If you wouldn't do free work in your position, why would I? I prefer you respect my time, career, and talents and do what's best for you, get a quote and suck it up. If you want something free, go ahead and use Comic Sans in Publisher and see how it turns out.