Look around eBay for the Feather in red/black pack, cost 25 cents each in the 100 packs from Thailand.
Astra SP are also pretty decent, found them in South Fl for about $11 per 100 delivered.
I tried $2 per blade van-der-shidteater from Walmart, or Eagle brand Dollar Store, but couldn't get through a whole shave without epic pulling!
Really, only good for 3/4 shave! WTF?
Feathers actually last about 10 shaves which is phenomenal considering Mach3 being a single use for me
Now Im sporting some mutton chops LOL looks rough.... rugged....