Rather than using asphalt or cement, which are two affordable materials that homeowners agree upon, what are some less expensive substitutes for driveway materials?
Well… That can be a tough question to answer. There are a few things a driveway can be made from. Besides the obvious asphalt and cement… You have stones, rocks/pebbles, rubberized platforms and even as crazy as steel panels. The limits of a driveway are depending on the creativity of the homeowner and the contractor. I’m sure if I had more time to answer this question with research, I can name a couple more ideas. Remember, just because you have an idea, doesn’t mean think inside the box. There are ALWAYS more ideas on the outside of that box. 
The materials are endless. I recommend gravel, or crushed concrete. It is cheaper per yard and lasts just as long. However, there can be a bit more maintenance involved keeping the grass and weeds out.
All the gravel materials will work for a driveway base but I would highly recommend that you degrass the driveways and excavate out at least 6" of the top soil. Topsoil has to many organics and is not good for compaction. Then roll the sub grade with your tractor or preferably a compactor. The next most important thing is use a Geo textile fabric. It is a woven cloth that not only creates a weed barrier but also will strengthen the ground under the rocks your about to place. It wont allow mud to pass through thereby saving you having to add more stone later. Then lay limestone (irregular shaped, never round, never smooth) that is about 2" x 2" for the first 3", the final 3" will be a smaller limestone or crushed concrete if you choose that has fines in it… the fines are important as they will sink down and further create a strong sub structure. Again roll your tractor over it a few times or use a roller compactor or even your vehicle but you want to make sure you have it compacted solid… Now you have a drive that will last for 10+ years without needed any maintenance. Art
3/4 crushed stone with fines. Tamped tight. Type 2a with Arts specs for ballast and fabric. It’s a good cheap driveway.