When I post eBay auctions, which I don't do very often, I usually pre-package the item
so that I can weigh the finished package and enter the details for the freight calculator.
That makes for a quick and easy checkout without back-and-forth over invoices. However, I
usually just have one thing listed at a time, so combining shipments isn't an issue. I
also do the pre-packaging thing because I'm usually busy with work and laziness (which
both take a lot of time and effort), so I plan ahead to minimize the barriers to my
getting the thing shipped quickly once the auction closes.
If I was a business and/or was listing a lot of items, then I'd probably need to
handle things differently.
There are plenty of reasons why a seller might not combine shipping, but a simple
"sorry, I can't do that because of reasons" is a much better way to respond
than a foaming-at-the-mouth rant followed by a rage-quit.
--
Mark J. Blair, NF6X <nf6x at nf6x.net>
http://www.nf6x.net/