My grandfathers would be shocked by a lot of things in today's modern culture. One is the price of bottled water. The other is the price of razor blades.
I can't do much about the price other than to suggest that you take grooming tips from Duck Dynasty. However, if you want them to last longer then I have a suggestion.
After you're done shaving. Just take the head and bang both sides against a dry towel (that's what she said). This will dry the blades and they won't get rusty.
From my own experience they stay sharp for at least 2 month. You shouldn't need to buy more than one pack a year.