I had an issue like that. For a package of dvds going to Australia it was prohibitively expensive. SO I did a stupid move and sent small packet it took like 3 months to arrive.
During this time of course the buyer contacted me concerned. To make the wait bearable I sent another tv series of Dvds however this time I made the buyer aware I wouldn't be sending the cases just the dvds in paper sleeves with the covers. Letter mail/ airmail.
They arrived in under 2 weeks and the buyer was very happy without the original cases so I would suggest asking the buyer if you could do the same thing. They can buy empty cases to put the covers in over there a hell of alot cheaper than you can ship the original case.
