You might not pay it but that's i have sold them for and Ebay completed listings are only a rough guide they vary so much, The Aussie brit exchange rate is 1 dollar to 55 pence stirling and the postage for that vase if it's under 2kg maybe £24.30 tracked, (44 dollars) the item price is often negligible, its the cost of getting it from A to B that's the issue. Now if i was in Australia and wanted to buy that piece of glass in the original post, what would i pay for it?, there ten a penny here but i would imagine in Australia there not, so supply and demand would dictate someone would pay what i sell them for, i have met so many lovely Aussies i would give them away if i could.
As to value, i do think it's an issue, people love to know what there treasure might be worth, as of yet though very few things i have come across on Ebay are worth anything substantial glass wise anyway.
I'm interested in glass history, i love it and collect it, sell it and i would help anyone on here if i could and knew what something was.