The original kayaks were built by the Inuit and Aleut "Eskimo" peoples of the Arctic.
Most of the cost of building a kayak is labor, but doing the work is part of the fun so we won't count that here.
Most wooden boats will actually weigh less than commercially manufactured boats. Because wood is structurally efficient, a boat built with it can be made quite light. The only real downside of wood is that since it is a natural material it is not necessarily consistent in its weight.
To build a striper from scratch you the minimum tools needed:
Table Saw or Band Saw, (Not required with the kits)
Thin Kerf Hand Saw,
A selection of clamps