Also, if you don't amortize in R&D, support, sales, and marketing costs into your total product cost model (COGS + business stuff + lights-on stuff) it's a sure-fire way to run out of money in a hurry. But, that analysis is more about product viability in the planning and development phase and less about equipment volumes once it's shipping.
I'm not saying R&D costs shouldn't be accounted, but that an investment + payback model should be used rather than an amortized cost model.
For example, you might invest $100k developing a product to get a $50k/year gross profit (income minus COGS), meaning payback in 2 years.
If you instead amortize that R&D cost over each unit sold over the 2 years, at the same sales projection and pricing, your costing will find out that you are making zero profit, and you will want to raise prices further to get some "margin". However, this is wrong, because you are forgetting that the income stream is still going to be there after 2 years, and it's free money at that point. Not to mention designs can be reused, team expertise got improved, etc etc. R&D is fundamentally an investment and not a cost. You have to constantly pay into it to keep your team expertise up to date, but it costs nothing to make use of a design that has already been done.