Robet Mann writes:

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    I saw something on one of the bee lists about this recently. I don't know
the reference, but apparently someone (I think it was Huber) confined bees
and fed them artificially, and then weighed the amount of comb produced. This
led him to the conclusion that it took about 6lb of honey to make 1 lb. of
comb, though he thought it might sometimes take a bit less. I don't know
where the higher estimates come from. It's obviously a very artificial
situation, and one might wonder whether the same ratio would apply in real
life, but like you, I have problems in imagining how else to do it.