I just finished Dragonsteel Prime. I read Way of Kings Prime when it was released (so: not recently). Dragonsteel (canon) hasn’t been written yet, so I’m not sure what you want to compare DP to?

Brandon has commented that Dragonsteel (Prime) never got published because the story didn’t really work. Some elements of it eventually turned up in Stormlight, of course.

I enjoyed both Prime books as a look at early versions of characters, settings, and magics. Reading WoKP after several Stormlight books, it was a little jarring to have a character die in Prime who is very much alive (as of SA4). DP didn’t do that to me; and as much as Brandon says there’s an early version of Shallan in that book, it felt like a wholly different character. I quite enjoyed getting to know Frost a little bit, and seeing early Hoid.

Shipping costs for the set bundles are listed on the campaign page. If you want add-ons, that will be extra and calculated later.

It does say somewhere that Dragonsteel will cover import duties for all international backers.

So really, the only unknown is shipping for add-ons. If shipping cost is a stress, maybe stick to the bundles with fixed shipping costs?