Shipping via container or even consolidated air isn't that great for a business - we average about 4% of the stock's cost for sea, and up to 15% for air shipments via a freight forwarder from the US to Oz.
Individuals face much higher postage costs. I recently bought a couple of BorgWarner T5 shifters (they suit the 3rd gen F-body T5s used in some 1980s performance GM-Holden cars). The seller was from TX and couldn't do enough to help me and make for an excellent buying experience - and I'm finding more & more US sellers are willing to bend over backwards these days for a sale, but that's another topic....... The small box weighing a few pounds cost me just over US$60 postage for USPS, when sellers of similar products in the US are offering free shipping within the states. I think a lot of it has to do with how sparsely we are populated when you get away from the capital cities (but that doesn't explain port-to-port costs!)
When it got here, i took my one out, and then I then sent the other half of the parcel on to my mate in New Zealand (our neighbouring country) and it cost me AU$75 for half the weight.
Their postage is very cheap though - He sent me a huge parcel of parts - about 15lb, a box the size of a 17" alloy wheel for a car, and it only cost NZ$25 (about US$1
But in answer to your question, I couldn't see freight adding more than $20 to each kettle or Q if weber shipped a container load of them here. The kettles are very popular in Oz, and the small Qs are becoming common too. The cheapest full-size kettle starts at about $280 in one of the 'big box' type hardware chains. You should see what it costs for briquettes, a chimney, or a looftlighter! Luckily there's a good guy in the west who imports & sells a lot of similar stuff for much more reasonable prices, but he's not selling the full weber range that the BBQ stores sell.