According to Beerbottlecollector.com, these are the factors that make beer bottles valuable:

Supply and demandAgeRarityConditionColorAesthetic appealEmbossing and design (labels)Category (what brewery, town)Size, shapeIndividualityHistoric significance

The rarest beer bottles are those made either during or just after Prohibition, because very few breweries were operating at those times. This auction lot consisted of two early Conrad Budweiser embossed beer bottles. They were described by Morphy Auctions as “very nice bottles with no damage.” Each bottle measures 11 1/2" tall. The pre-auction estimate for the lot was $100-300. The pair shown here sold for $300 (not including buyer’s premium) in March of 2015. Sold for $420 (not including buyer’s premium) in March of 2015. Sold for $300 (not including buyer’s premium) in March of 2015. Sold for $2,700 (not inlcuding buyer’s premium) in March of 2015. Sold for $180 (not including buyer’s premium) in March of 2015.