Well, I am so cheap! Just realized that, thank you. I use up the blade till there's almost nothing left, then I sharpen it!
The old blade goes in an empty blade container that I saved and marked (literally) USED so I can tell the difference. I re-use them when I cut fleece and paper because I find that both ruin the blades.
There is very little that I actually throw away. Yeah, I'd like to say frugal but, truth is, I'm cheap.