It has three high power voltage converter circuits which are needed for it to support USB Power Delivery. Those are more expensive than the batteries and no other device has three of them.
Lithium-ion packs are measured at 3.7 volts, not 5.
Lithium-ion packs are measured at 3.7 volts, not 5.
I think this is a neat implementation but there is no technical justification for this price tag, and the idea is far from unique. Looks cool though, and I guess for some that's all that will matter.
We are also using ultra high efficiency parts and may also increase the power to over 100 watts if we can get it approved/ make it safe.