Player support for video DVD stored on a CD-R?
If you're authoring DVDs to be played on DVD players, then this won't work. I checked it out way back when there was a significant price difference between CD and DVD media.

If the end users are all going to be playing on computers you could send them instructions on how to open the DVD media folders, but realistically what you'd save (if anything) on media costs would be eaten up in time spent answering queries from disgruntled users who can't get it to play.

Just for reference - the first site I saw when I searched for "bulk DVD CD media" has 100 DVDs for $19.90 and 100 CDs for $18.90. So the difference in price is 1¢ per disk.