My friend and I made a bunch last year. He got the wood and shaped it for free at his work and I got the spool kits, dowels and triggers from 40UP. Used screen door springs cut down for springs. Made the trip wire ourselves and the tube from brake line. Bought florescent for flags from craft store. Got the line from R&W Rope in Fall River (Uncle Macs). All told the 5 tip-ups probably cost $15 a piece.
Also made the "coffin" to get the gear out there.