If you are going to retail, then you might sell to the wholesaler at 2x the COGS. They will turn around and sell it to the retailer with some markup, and the retailer will mark it up again, quickly getting the retail price to 4x the COGS. If you are selling online only, you can sell for less because you don’t have the overhead of wholesale or retail, but it means that you may never be able to sell retail in the future because they don’t like it when you sell online for cheaper than they sell in stores.
Many of us develop things for one of two purposes: to hack something cool, or to sell something cool.
If your goal is to sell the thing you are making, then a lot more thought and effort is required.