Can someone explain wildly varying GSP shipping costs to me? What's the variable factor here?

[imw_consulting_ltd]

I've listed an antique bible ( item #275512826234) on here, which is being sold via the GSP.  A potential US buyer is querying why they're being quoted a shipping cost of £192 for it when a very similar-looiking bible (item #335105631606, also in the UK, also being sold via GSP) comes up with a shipping cost of £41 for them instead.  Dimensions seem roughly the same in both cases, mine weighs in at 5.6 kg when packed and the other seller is giving a figure of 4.97 kg (though admittedly that seller hasn't indicated if this is the item weight or packed weight.)

Don't get me wrong here, I'm not expecting both listings to come up with the exact same price for US shipping, if mine worked out at, say, 50% more than theirs then I'd put that down to the limitations of the GSP and see it as a win-some, lose-some situation.  But five times as much?  It's unfathomable to me.  Is it to do with crossing the 5kg barrier?  I know that's enough to move you into a different band with most UK couriers, but not to this kind of degree.  I'm wondering if I've just done something wrong with my listing somehow.  But I've entered the exact weight and size of parcel.

Any ideas?

[cobwebcottage · Accepted solution]

There is no rhyme or reason for GSP prices which I can make out. I have had similar before and found that if you revise the listing and change the category it is listed in, this can work out cheaper. If the person is still interested in it, change it to the books, comics and magazine category and see if that will reduce it.

[ett1954]

GSP costs are not just shipping costs related to weight.  They include dimensions, insurance (dependent on value), taxes and import duties (online sales taxes in the US vary according the state which the goods are being shipped to and these vary between 0 and 10%).  Category, currency exchange commission, and a remote location may also be a factor.

[imw_consulting_ltd]

I'm such a fool, at the time that the prospective buyer originally suggested the GSP shipping cost was too high I didn't have any weight or dimensions included on the listing so the GSP would've had less information to go on to make a calculation.  So at that point I went in and added the weight and dimensions to see if it reduced the cost for them.  But it appears I tried to type "5.6" into the "kg" input field, which wouldn't be a problem except it doesn't accept decimal points so changed it to 56 kg without me even realising.  No wonder it was expensive!

Anyway it was only when I went to change the category as per your suggestion that I noticed this mistake, and now I've changed it to say 5 kg 600 g it says £49 which is more inline with the other seller's bible.  I still don't know if this is more or less than it did when the buyer originally queried the postage cost as he didn't say what the eBay figure was at that point, but either way I don't think it's that unreasonable any more. 
Cheers!