I pride myself in being cheap.
If I have something fragile, I usually put some cardboard around it first (an old box that something was shipped to me in breaks down nicely, I also get a lot of boxes from when I buy box lots at auctions). After the cardboard I use good 1/2" bubble wrap. Of course, like you said, there is usually that void to fill. To fill this void, I use shredding. If you don't have a shredder they are not that much money for a small one, you can usually get them for around $10. I get many + fb's about my great, safe shipping. Just make sure it is strip shreds, not the cross-cut
The shredding might be a little heavier, but an extra ounce usually doesn't affect the cost of the package unless you are exactly at a specific pound mark. You may not think you have things to shred, but believe me once you get into the habit you will end up with too much lol... I never noticed how many things printed wrong or how many times the kids actually printed their cover pages for their projects before getting them "just right". Junk mail is always fun to shred. Just make sure you're not shredding your bills - can't get rid of them that easy! Oh and yeah, there's always that identity theft issue
I understand that you may want things to look professionally packed as cavaleriesoldaat said, but I don't think this is too bad... maybe it's the mid between newspaper and peanuts. One of these days maybe I'll become high-volume too and will be able to afford the peanuts