Yeah, it's kinda crappy. I didn't get a chance to go to the brewery on Darkness Day, which is about the only place you can get it for $18 a bottle. I bought like 4 bottles from local liquor stores at $25 a bottle the next day before they were sold out too, so $40 isn't actually too unreasonable for someone selling. I have two bottles left, and I just posted a trade post for a couple different rare bottles.
Since everyone that bought at the brewery is limited to 6, and the stores that sell it limit people to 1 or 2 per person, you might be pretty hard pressed to find someone willing to trade one for $18 worth of stuff, IMHO.
Not trying to be a dick, just realistic.
"If you are flammable and have legs, you are never blocking a fire exit."