hobbytoolsupply via Amazon offers this Set of Five P-38 G.I. Can Openers for $4 with free shipping. That's 80 cents per can opener and the best price we could find for this quantity.

Update: As a reader notes, hobbytoolsupply also has this G.I. P-38 Can Opener 15-Pack for $5.08 $4.90 with free shipping.