If you're looking to expand this into a business, you'll generally have to start doing things that are outside of your immediate level of comfort, enough to grow of course.
If this is something that you only like to do as a personal hobby, then I would hesitate, because the worst thing would be for you to agree to it, and then something goes wrong and/or they hate the product.
Then again, it's not like a prom or wedding, something that's really special and unique, it's just a business conference shoot. So screwing it up would be bad, but not ruining somebody's super special day.
Up to you, but if you don't feel like you have a pretty high chance of delivering a product they will be proud of, that's a good reason to not do it.
Also, there's likely a reason they can't find anybody to do it for less other than you. As a freelancer myself, when people come to you saying that they can't find anything in their price range for a service, it's usually because they are clueless about the actual value, or they are hardcore cheapskates. Both kinds of people typically are not good customers.