Wow, those must've been some small $5 bundles! It seems like there's always a guy selling wood out of a wheelbarrow or shed near most campgrounds. If you can find him, that's usually the best deal. Second best is usually Home Depot or Lowes (that wood has been kiln treated so it's okay to move if there's not one nearby). That will at least get you a large bundle for $5-$7. Then the campground host if applicable. And last the gas station/convenience store bundles. If you get stuck going this route, making a couple of stops to try to find ones that have oak instead of pine will help you get better value.
Personally, I never skimp on firewood. The most enjoyable part about camping is having a nice fire. So even if you get stuck paying $5 per small bundle, it's still worth it to me. But of course it's always nice to get a huge fire for cheap.