I boosted my speech to 70 and picked the 5 perks and the lure perk, Adrienne at Warmaidens will now sell:
1 Iron Ore = 4g
1 Iron Ingot = 11g
Firewood is of course free to make. Thus a batch of arrows is the cost of an iron ore or ingot.
At a high enough speech skill, I was able to sell the arrows for 1g each. Thus:
4g -> iron ore -> 24 iron arrows -> 24g -> 20g profit each batch
11g -> iron ingot -> 24 iron arrows ->24g -> 13g profit each batch
So if you make your rounds around all the blacksmiths in Skyrim, the vendors restock and you can make infinite money.