Mike; I know it's a little bit messier, but if you mail your cards in the flat rate priority cardboard envelopes... it's much cheaper than in the more convenient priority boxes. Up to one pound costs $3.85. Even if you send two separate flat rate envelopes to the same address, it might be cheaper than using the box. Also, if you wrap the cardboard envelopes with the sturdy Priority tape that your local post office supplies, you'll find that it prevents the carboard envelope from being accidently ripped open.