I'm guessing this topic has been visited and revisited over and over on SMC, but I'm still new here so I'll ask my question anyway.

I flatten my Norton and King waterstones on wet/dry 220 grit sandpaper on a granite surface plate. Now that I'm sharpening much more regularly, I'm going through sandpaper sheets at a noticeable pace. I'd always heard that in the long run sandpaper is more expensive than other methods, but that was less relevant when I was sharpening less frequently.

I did hear on this site that folks discouraged me from looking into the Norton flattening stone, so my plan is to continue with the wet/dry paper (plus, I already have the surface plate). The five-sheet packs are 7 or 8 dollars, though. I want to choose one brand and buy the largest pack I can find (probably 100 sheets), so I don't want to get stuck with something that doesn't work well.

Who can help me make sense of the variables here? It looks like silicon carbide may be better at this grit than aluminum oxide. Agree? This is just for the waterstones. For me the other attributes that matter are: easy to reuse, gets flat again the next time on the plate, lasts through several flattenings, doesn't slide on the plate, and resists bunching up. Finally, I'd like to get the price down below $1 a sheet.

Any other wisdom is welcome, even the contrarian view on the sandpaper method.