Battle >>> sells Bloody lance head for 5m
Crafter >>> buy the head for 5m
Crafter >>> crafts and sells the champion for 6
Battle >>> buy the lance for 6

in this scenario the battle payed the lance 1m... 1m for the crafter work

if you put a materia cost in the calculation a gather would earn x gil for his time\work

the battle would pay then 1m + the gather cost...

thats how the economy works, the final user of an item will always pay who works to make it.