Mighty nice of you to be "giving" away what those in the industry count on to feed their families. Have you given any thought to tax law? If you're selling, you need a tax ID in the US. If you give a DVD, you've manufactured product and are required by law to pay tax on the "compensation for services" that you described. It has been tax exempt to allow digital files to be downloaded on the internet, this is about to change but as yet is still true as far as I know. The reason is that you have not produced a physical product...that one copy at $0.21 changes everything!
So, if your friends paid you $200 to cover your expenses and you sell 1 print...even at .21 (or $0.09)...you're required to pay tax on the entire amount you got for shooting the event. Even at that minimal amount...$200.21...States in the US are willing, in this economy, to prosecute for not paying the tax and this means that they can assume (and WILL assume) you've been doing this for 10 years and hit you with whopping fines and backtaxes! Welcome to the wonderful world of doing business!
This is why pro's charge what they do for their work. Insurance, overhead, equipment costs....yada yada yada. And yeah, the desire to feed their families.