Price is not the main reason many people don't buy CR123A for their flashlights. The market will buy a superior product if the price/performance ratio is lower. The main reason CR123A is unpopular is that CR123A is not ubiquitous in other electronic equipment and not in stores. Thus, people don't buy. Thus, electronics makers design around other batteries. Thus, it's not ubiquitous. Thus, people don't buy. Thus, electronics makers design around other batteries. Thus, it's not ubiquitous.... Thus, we have the vicious cycle.

Some may say CR123A is not ubiquitous because it's more expensive, but actually it's the other way around also. CR123A is more expensive partly because it's not ubiquitous. As an analogy, if I made a battery that was 20 times better than CR123A, I'd have to charge $1,000 per battery until it could be produced on a scale so massive that it was a standard. People likely wouldn't show up in masses to help me improve my scale. So, the price would have to stay at $1,000 per battery in order for me to recoup research and development expenses. In contrast, if people bought more of my battery or if I had patient venture capital funding, I'd be able to charge less, and I'd have to charge less because I'd have competition (e.g., from Chinese manufacturers). CR123A is on the cusp of seriously rivaling AA (e.g., the price/performance ratio is almost lower than AA), but when large organizations like the ARMY move to AA, it's a setback.
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If you're reading this, it's too late.