Several years ago I bought a year's supply of Mach 3 blades from my local Wallmart. The packages were sealed in hard-plastic, anti-theft containers, and then displayed inside locked display cases. I of course paid full retail.

When I tried the first one, it literally wouldn't cut a whisker on my face. Even 2-week old real blades cut better than these. Walmart replaced them, and the replacements were the same. I now see very clearly that they are fakes, from pictures on this site.