There is no real way that I know of to find an average, and I could be wrong about that. Certainly you might find some analyst reports on public companies in a certain product category where it makes sense to assemble these averages, but for private companies, I do not know how you could assemble this data.
I think trying to arrive at this kind of data would also be very misleading, because it would depend upon how you want to use it.
If you are a brand, or vendor as it is called who sells wholesale to a retailer to resell at retail, or also called the manufacturer (although this can be misleading because so many products are produced by co-manufacturers, or 3rd party manufacturing companies that produce private label products), then this number will be specific to the category in which you sell.
In general, products with conventional and more commodity-based ingredients might make more margin than a natural or organic brand, because cost of goods sold (COGS) for these latter products are generally in the 40-70% range, at least in my experience. Conventional may be closer to 30%, but again, that varies highly with the product category.
As a goal, I shoot for 40% or less in COGS, so my gross margin is 60% or better, and I try to shoot for a 20% net profit margin (when selling through retail), so my remaining operating expenses would be in the 40% range. But, this is at volume, not at startup, which typically sees higher COGS and operating expenses, so much lower or negative net profit margin.
I know as a general rule of thumb, which I try to follow, CPG’s seek 20% net profit margin (when selling through retail).