They are canny heavy as theres about 40 give or take, as said they are about 25Kg's in total (heavier than royal mail allows iirc as the sites down at the mo) so would need sending in two boxes...i bet you'd be looking at maybe it working out to something like a £1 a mag. Thats a very rough guess mind and should be cheaper.
Will get a proper answer once the sites back up 
Where abouts are you btw?