I'm an artist and find that recycled sketchbooks are unaffordable. The best way to get your money's worth is to use every possible inch of space. In art class the person I sat next to left big open spaces all over her sketchbook and had to replace them every few weeks I think it's important to make use of what we have.

I was at a concert last night that had live art projected during the show by the artist Jim Woodring.  Just like you recommend, he used every corner of the screen in his drawing.

He has a blog, I'm hoping he'll post the final drawing image there:
http://jimwoodring.blogspot.com/

I am also an artist and it is amazing how much paper can be wasted in the creative process.  However, there are also many other options to reduce waste due to a large number of sketches besides just using every inch of the paper.  There are many sketchbooks that used recycled fibers in the paper and that do not use environmentally harmful chlorine to process the paper, although, as you point out, these sketchbooks are generally more expensive than standard sketchbooks.  Besides using every possible space of the sketchbook, paper that has been drawn on and that is not wanted anymore can be repurposed by making other crafts out of it or even ripping it up and using it as the "grass" in Easter baskets or as confetti.  Once the paper has truly outlived one's personal use, it can be recycled again!  I also always try to avoid buying new sketchbooks until I have completely used my current one up. There are so many ways to make art a more sustainable hobby or profession,  and an awareness of the infinite different recycling and repurposing options will also make art less expensive.

How about making your sketchbooks out of paper that you find in a computer room recycling bin  that still has one blank side?  That's what I use to make my field and lab notebooks.

I have learned that companies are very receptive to letters from customers. Just last week I found out from a speaker at my school that Apple changed their packaging philosophy after many letters from consumers. Maybe you could reach out to some other artists and start a letter writing campaign to companies that manufacture sketchbooks, requesting that they increase the amount of recycled sketchbooks they produce and try to make them more affordable. Also, if you and your artist friends always purchase recycled sketchbooks and spread the word, these companies will begin to produce more of them due to supply and demand.