I’m just looking for a list, maybe even ranking things on a log scale. maybe categorically also. i think it’d be a worthwhile collaboration.
note: not really looking for historical relics, or other things of that nature. more along the lines of commodities. however, it would be interesting to compare an ounce of rare earth element vs a faberge egg.
(please keep quippy one-liners like “a mother’s love” or “common sense” to a minimum.)
Saffron’s usually a safe bet. Americium, too.
Californium will cost you upwards of 10$/mg. So if you wanted to mint some into a silver dollar it would cost you a cool quarter mil.
And would kill you by next Thursday if you kept it in your wallet.
I’ve seen it argued that antimatter is the most expensive substance costing well over a trillion dollars to create an ounce.
ETA: it’s mentioned on antimatter’s wiki page
Saffron is only (ha ha) around $1,000 a pound or so (according to wiki anyway). That’s nothing, really. Good old gold, for example, is now around $1,000… per ounce.
Americium is a ‘better’ choice, it’s around $1500 per gram or $653,385 or so for a pound.
Californium as tvvat mentioned is even better. at $10 a mg it would be around 4 million bucks for a pound (not that we produce that much on earth anyway).
But if you’re allowing exotic things like californium I think antimatter wins. If you want just plain old anti-electrons (positrons) the estimated cost would be around $25 billion for a gram. If you want the good stuff, anti-hydrogen, bump it up to $25 trillion or so per gram.
Edit: mixed up my millions and billions and trillions
It does have the distinction of ranking quite highly in the organic category, however. I wonder how it compares to various illegal drug (or legal but exotic medicines).
I have no firsthand experience of the price of any illegal drugs, but according to google:
Marijuana - $223/ounce ($3,568 per pound)
Heroin - $88/gram ($40,000 a pound)
Cocaine - $20,000/kilogram ($44,000 per pound)
MDMA - $100/gram ($45,359 per pound)
Of course those prices are incredibly variable depending on which site you read, and I have no idea of the accuracy of them at all. Still, it looks like illegal drugs easily have saffron beat.
I would be very much surprised if there aren’t pharmaceuticals more expensive than $100/gm
How about an ounce of oil paint . . . on Jackson Pollack’s *No. 5, 1948, *the entirety of which has sold for $140,000,000.
Ummm…I’m not sure if this is your math or just from the website(s) you got the numbers from, but something’s not right here.
Heroin, at $88/gram, would equal $88,000/kilogram, over four times as much as Cocaine, and yet…ther per pound is $4000 less? The actual amount is $193,600 per pound…unless the $40,000 per pound is the right number, in which case the heroin is ~$18/gram…which can’t possibly be right. I mean, I don’t know a lot about drugs, but that seems damn low for a drug that’s pretty risky to get/make.
And if MDMA is $100/gram (MDMA is ectasy, right? If so, then that sounds right, since a friend bragged to me that he got a pill for only $20 the other week, and it was probably a couple hundred mg, yes?) then it would be $220,000/pound.
This whole thread gets very confusing to follow when people are freely switching between metric and US units, and posting bad conversions. So let’s all just stick to metric from here on out. It’s the superior system, and well all know it. 
Clearly, given that your conversions were all messed up :p. You divided where you should have multiplied, or possibly the other way around.
You’re right in spotting the discrepancy, though, but it’s the cocaine that’s messed up.
$20 000 per kg = $9 000 per pound
or, alternately
$44 000 per pound = $97 000 per kg
(I have no idea which, if either, is correct).
Well if you’re doing illegal drugs 300 micrograms of LSD street price is approx $15.
so 1 gram = $50,000 and 1 Kilo = $50 Million dollars…
I did hear once that black widow venom is the most expensive liquid in the world. The reason given was that the spiders are so small, and produce such a small amount of venom, that obtaining the venom (by “milking” the spiders individually) was a hugely labor-intensive process.
The figure given here is up to 100,000 spider milkings to produce one gram of venom, which would take about a year to do. So, if this is some lab jockey who you’re paying $30K per year, you’re talking about $800,000 per ounce just for that labor; that neglects other incidental costs, like finding the spiders, feeding them, storing them…
From Geoffrey Miller’s Spent: diamonds are $1.25M per pound, while LSD is $30M/lb and a human egg is $4.5 TRILLION/lb.
Compare that to a laptop at $204/lb, a car at $7/lb, and a house for $2/lb.
If you want to open the list up to organic consumables…
White truffles will go for $100k/lb
Vicuña wool gets $1800/$3000 a yard. (About 3’ by 4’.)
Last time I checked (and this was a few years ago) tritium, at US$30000/g, was the most expensive substance on the free market. Given that tritium production facilities are becoming increasingly limited (the Savannah River facility used to be the main producer of tritium in the United States) and has a relatively short half-life of 4500 days, the cost of tritium was projected to exceed US$100000/g before 2020, and would cause significant constraints on maintaining the Active (nuclear) Stockpile by 2015. Tritium does not occur naturally on Earth in recoverable quantities, so alternatives, like using a Farnsworth-type fusor for tritium production, are being investigated for viability.
The problem with anti-matter isn’t just that it costs so much to produce it–positrons are a by-product of beta plus decay–but that it is very difficult to confine it and combine into any useful substance or quantity for any duration of time before it interacts with its complementary normal particle and disappears in a shower of photons. The majority of anti-protons produced in a particle accelerator collision disappear almost as soon as they are created. Even if we could make anti-matter and store it, it would likely be of questionable use for any terrestrial application, as the resulting energies are just too high for most thermodynamic cycles.
Stranger
Well, if you consider Higgs Boson to be a substance, so far it’s hundreds of billions of dollars, and we got none. 
Of course, that is just cost of manufacture. The market price could rise from that.
Tris