We use 'triangle' style flashers here in tidewater areas of the Columbia and bays up and down the coast in Oregon. Companies like ShortBus here in Oregon have refined them to a fine art. No internal spinning 'wings' though. Basically for 'dirty' shallow water fisheries 30? feet and under. We rig them typically with main line (65# braid) down to a swivel. 12" to 18" lead dropper on a slider on the main line, on something stiff like one strand of phone cord wire to a clip with 8oz to 16oz lead depending on depth and current flow. Back to the main line swivel....12" to 24", depending on personal preference, of 150# mono or titanium wire to the front of the flasher (keeps it away from the lead on the drop) then 36" to 60" of 30# to 50# fluoro leader with a swivel (ball bearing or chain) in the middle, to plug cut or whole Herring, anchovy, or possibly a spinner. In tidal areas they are fished trolling right on the bottom on the ebb and somewhat suspended on the flood (tidewater Columbia). There is a transition going on here to 11" flashers like the HotSpot with a size 3.5 spinner 24" to 36" behind on 50# fluoro. They are rigged as above, but the lead is typically on the heavy end (16oz) and attached fixed to the terminal swivel on the main line. People here think they need to add an angled fin to make them work in the current, but we use our HotSpots (our favorite Clear UV Chameleon with Silver Crystal Flash tape) with really good success.
We seldom use 'Triangles" in the ocean unless we are fishing in less than 30' of water. Always use HotSpots and usually downriggers. Hopefully, the above gives you a little 'application' information to help put things in perspective. As far as price point, a 'quality' 8" triangle flasher with ball bearing swivels on both ends from somebody like ShortBus is about $12.00 USD, $8.00 on sale. $30.00? Never happen here.
For your Ocean fishery off the Island, I personally wouldn't bother.....................................but then again, banging the bottom slow trolling for Halibut, might be just the thing.
Stay Safe. Have a Great Day!
Tuna Maru