My observation on dry molasses is that you get a bag with 49 pounds of corn cob trash and 1 pound of molasses. I could be off by a pound either way, but to me that isn't a deal.
Farm co-ops sell it by the pound. They will quote you today's price just like you are exchanging dollars for pesos. Last price I heard was $0.09 per pound. A gallon weighs 10.5 pounds. So a 55-gallon drum (575 pounds) would cost about $52.00, but you have to bring the drum.
I believe you're right about the liquid being a far better deal if one can buy it in bulk and if one has a way to apply it. It would be great to coat grain meal, oil seed meal, alfalfa meal, or lava sand with liquid molasses and then spread the coated material, but I don't think it's as easy as it sounds. Maybe someone on the forum has experimented with that idea, perhaps by diluting the molasses.
There should be some seasonality to liquid molasses prices, with the lowest prices typically coming at harvest time. The Lousiana cane mills have just started molasses processing for this year, so one would expect to see the lowest wholesale prices somewhere in the Oct-Dec time period. I imagine most mills run on natural gas, so gas price in relation to cold northern weather could affect the later part of that time period unless the mills hedge or forward contract their gas purchases (which they probably do). The beet molasses mills also should be in production about now. Most retail buyers will not have much choice of where they buy their liquid molasses, but I still would be on the lookout for diluted material. Product density will vary among grades, but 10 gallons of water in a barrel of molasses could be a profit kicker for the unscrupulous dealer. For those that live in the southern U.S., their wholesale blackstrap products probably come from the South, particularly Lousiana. There could be some Mexican source in there also, especially in the southwest and California. For those that live in the northern U.S. or Canada, the sources are more likely from Canada mills or from Plains states sugar beet processors. Supply origins probably shake out according to shipping costs most of the time. That's about it on the molasses topic, except to say that Dancing Deer Baking Company in Boston makes about the best molasses clove cookies I've ever tasted. They're hard to resist.