Portable power packs are crazy cheap these days. You can get a 20,000mAh pack for $45 quite easily. They are almost always Lithium Polymer based, and are very s

Portable power packs are crazy cheap these days. You can get a 20,000mAh pack for $45 quite easily. They are almost always Lithium Polymer based, and are very small and light. I have had one sitting in my bag for almost a year now and it still has most of its charge. What I don't understand is why it would be so hard to just scale those power packs up a little bit and slap a normal 110 volt A/C plug on them? Wouldn't that essentially be a super efficient, light weight UPS? I did a bit more digging and I found a couple of portable power packs that offer this sort of functionality: https://www.nytimes.com/wirecutter/reviews/the-best-portable-ac-power-supply/ https://www.nytimes.com/wirecutter/reviews/the-best-portable... What I don't understand is why they are so expensive, and why they can't seem to scale them up to the same size as a normal lead acid battery UPS?