What I really need is some idea of the cost of a beef carcasse in the mid-Victorian era. I can then relate other prices I know to that. Presumably information like this is available, but I've not got very far - I got a victorian maths text that gave three different prices for a cow in three different sums, but I'm pretty sure that there is no real world connection, the numbers were just used to make the sums work.
Maybe something like a naval history, presumably navies bought meat in bulk? Anyone got any thoughts?
Later It occurs to me I'm looking at this wrong - it's only the big rich dragons that will be eating whole cows, your average dragon in the street probably just buys a goat or a few pounds of beef. So I'll work it out from butcher prices, which I already have.