WOW!Strangely enough,I think that I have dealt with this seller before and I asked him why his postage was so high and if I recall,he did offer a lower rate.Perhaps you should email him like I did.
I think that the new way which eBay sellers have to list,has caused some problems as well because now I think that you HAVE to say how much postage is and I think that many sellers are going to postal links to get an average cost and are using the posted charges verbatim without regards to wondering if this is a bit too high.In plain English...they are guessing!
I know I had one seller state that postage to here was $16.85!!!...and I emailed him and he could not believe that it said that in his ad and he "only" charged me $3.00 for shipping.
Drop dave_sam a line and ask.It won't hurt.