I got this for free when I ordered my stuff from them, it has a magnetic bottom. Very small and compact but I'm sure it can hold a ton of blades

I actually spent $1.00 on an "official" blade bank last time I bought something from Em's.
I use an Altoids tin and keep in away from reach of little cousins.
I quickly found out that putting the blades in the back of the new blade pack was just a new way to throw used but still sharp blades all over your vanity drawer. .
+1, this is a case of over thinking things. Some even have used blade slots in the bottom, like feather and Merkur.Nobody has mentioned using a plastic blade dispenser. I can get six months worth of used blades in one dispenser, then I tape it up and chuck it.
Metal spice tins are a good idea -- just recycle all the metal at once, that way. I actually spent $1.00 on an "official" blade bank last time I bought something from Em's. Sometimes I'll spend $1.00 to be mindless. . Metal. Safe. Recyclable.
+1, this is a case of over thinking things. Some even have used blade slots in the bottom, like feather and Merkur.