I think it's a good idea because it fits a need or fear that many people have. I would consider getting them (Vortex PST) if they were relatively cheap. I won't know for sure if I'll use them, but if the cost is low enough I'll roll the dice.
I've always wondered why scope companies don't do a better job of offering turret cap options, even if it's a secondary purchase based on preference. Although I would prefer the scope companies come up with a simple turret lock, i.e. sliding button or something.
Your production costs shouldn't be too bad once you get the specs for the scopes you want to support. I thought 3D printing was cheap and molded hard plastic even cheaper via China.
I wish the prototype was made of black material vs white. It would be more visually appealing and help with the first impression. The white makes them look bulky. I know it's just a prototype and most likely wouldn't be white, but first impressions do matter. Maybe consider going with a thinner wall as well, to reduce bulk. Looks thicker than is needed.
Given your turrets rubbed the inside of the scabbard, I assume these naturally would rub and try to twist as well. Are the bungee chords enough to keep this from happening...not even a little? I think I saw in the video the bottom was flat. You could make it slightly concave to have a better seat against the scope tube and reduce the likeliness of it twisting when rubbing against a scabbard. Just a thought.
From a pricing perspective, I would put them close or just above scope caps, since that's a frame of reference for most hunters. If your production costs allow for it.
Marketing, sales channel etc...that's the easy part if you have a good product that resonates with customers.
Maybe reach out to guys who have made other one-off products in the industry. TriClawps comes to mind. Outdoorsmans might have good advice as well since they produce their own products.
Other ideas....how hard would it be to print on it? You could offer putting a customers name on it, a slogan (Aim small, miss small) or other useful info. How about "Ear plugs on!" I've regretted not remembering to do that when I had a brake on. Or a windage chart, which can be viewed once the cap is sideways. Food for thought.
