Not sure if i would agree. There are many many cultures which simply do not develop sea-travel, because they simply do not need it.The Avari we met so far are nomadic hunters, now there seems to be one culture, of Avari or Nandor which are farmers or at last quite sophisticated Vintners.They still do NOT need sea-travel.Not if their northern neighbours do it for them, such trade and sea-travel cultures are quite well known, most famous the Phoenecians.
Second... you say the ships do not pay off. Do they have to? The Sindar may not be anarcho-communists as Corey puts it, they seemingly DO have a gifting, sharing & bartering economy of sort.They do not necessarily need to do trade for anything to pay off.They would still do it to get stuff they would like to have and have not by themselves, such as plants and products from plants which grow in a warmer climate (or dwarven weapons!).
Second , the Falathrim do not build ships because they need to.They do sea travel for the sake of it, because they love it, because they love the sea and love to build ships, they do not NEED any other reason and nothing needs to pay off for them.They are just natural born ship&ocean enthusiasts!
They still would use these knowledge and skills for practical purpose such as trade and transport if it suits them though...