I think your low balling yourself. $100 in parts with more to possibly buy..
Say you go $150 in parts. Now what's the labor time to build? Now add all the time spent answering questions and emails, tech support for anyone who is having issues, packing and shipping, taxes (if you go that route), paypal fees, inventory and supplies orders.
With my tail lights I never thought about the above until I'd already put the price out there. I know they are expensive, but if I started again I would have charged more. I never thought of everything that is involved with it all. The labor itself to build the light is one thing. Add everything else and it's eye opening. Ive had a couple small price increases over the years, but that's mainly due to various circuitry price increases. My big saving grace was I bought about 30,000 lumileds LEDs at wholesale for pretty cheap a few years back.