How do I calculate the market value for a limited edition beer (1700 bottles only)? It cannot be bought anywhere anymore except from private collectors. The beer in question is the Opeth XXV anniversary imperial stout.
The only way to know the price for sure is to sell it and find out the price at that time, preferably at auction.
The only way to price a rare item like this without selling it is to mark it to market. You need to find a number of comparable bottles of special edition beers with similar collectors' markets and use the prices of those bottles to calculate the current price of that bottle. The more similar the comparable bottles are in terms of time since sale, qualities of the beer (style, ABV etc.), number of bottles produced and size of "following" or number of collectors, the closer your price will be to a realistic price. If it were really valuable an auction house such as Sotheby's or Christie's could be employed to do the calculations for you as they are quite involved. Note that marking to market only gives a guideline price at a moment in time as prices can fluctuate wildly in collectables markets.
The basis of this pricing model is the pricing of any liquid commodity or financial instrument.