I thought it was a tad steep too. And the seller would never have gotten a sell from me. Me either... i totally get the fact that the buyer agreed, but even if the buyer asked afterwards and the seller said no, the seller stuck them all in the same box, that's what would have did it for me.
and technically the seller DID combine shipping by putting everything in one box, OP was grossly overcharged!
If the seller said no and shipped separately, it may have been a little different, but we all know "why" the seller put everything in the same box. It just seems really selfish to me.
If it ain't broke... fix it til' it is.