I've found Linnen Cloth to be very profitable...Desynthing Tonberry coats for anywhere from 3-8 linnen threads Coats on Fairy go for 400-600 gil 1 stack of cloths sell for about 60k-65k its a tough desynth but with moghancments its fine and if you're standing in the right direction you can get 8 out of 10 desynths yeilding 1-2 stacks of threads...
Mass produce too! but sell in various locations...when i max out on GP i usually keep synthing the item if i can make it and put it less than AH price and just sit by Cloth guild till i get home from work.
Good times!!