This summary assumes you will purchase all materials and shows where the cheapest place is to purchase crafting materials for Horn Arrows. This is how I roll because I have only a couple hours per day to play, if lucky.
Earth Crystal
Buy stacks from San D'Oria AH for about 500 per stack (42 ea)
Arrowwood Lumber
Dehbi Moshal in the Woodworker's Guild in Al Zahbi for about 8 ea.
Cauzeriste in the Woodworker's Guild in N. San D'Oria for about 18 ea.
San D'Oria AH for about 1,000 (83 ea.)
This can be crafted as well.
Bird Fletchings
Windurst AH for about 2,000 (20 ea.) but stock is rare.
Jeuno AH for about 3,000 (31 ea.)
This can be crafted as well.
Horn Arrowheads
San D'Oria AH for about 15,000 (152 ea.) but stock is rare.
Jeuno AH for about 30,000 (304 ea.) but stock is uncommon.
This can be crafted as well.
My results:
7/25/2009 - Placed 6 stacks on Jeuno AH for 3,000 ea (normal price is 2,000). No stacks currently for sale.
Potential Revenue: 18,000 (3,000 per stack)
Break Losses: 1,491 (248.50 per stack)
Cost of Materials: 9,198 (1,533 per stack)
Profit: 7,311 (1,218.50 per stack)
Yes I made a small profit. Please note I did not synth these to make money. This was a recipe I used to get my Woodworking from lvl 46 to 49. Assuming my arrows sell, I will come out with a little profit plus I leveled my craft.