What goes into that cost? Well here are some factors:
Costs I do NOT include would be shipping costs if the bottle was acquired via a trade; generally both ends of the trade are out of pocket the same amount, so it's not fair to include that, or gas costs if I drove to Buffalo and back just to buy the beer.
As an example, I have Stone Imperial Russian Stout here - the initial cost was only $4.99 US per bottle, so far so good. But then shipping from Southern Califoria to Niagara Falls NY worked out to roughly $3/bottle US for the whole order; then I paid duty of 28% bringing it across the border; then there's the currency conversion (runs 10%-12% lately, although some of the beers in my cellar came in around 18%!). I'm low-balling myself by making that $11 CDN ... $8US plus 28% times 110% conversion is more like $11.25.
But then some beers I get from my sister, she brings them through customs, no shipping, no duty, all I do is work out the currency conversion. I try to be fair, but it COSTS getting west coast US product to Ontario - if it seems too high, I am always happy to drink my own beer. I just want to be above-board about why the numbers are what they are.
This also means from time-to-time there are different costs for the same beer - this just means I got more and it was more expensive or cheaper.
I know these numbers seem high, but anyone who has done any trading knows the beer is usually less than half the cost - shipping etc. usually comes in higher.