I forgot it has a battery as well, so add on the extra power and charging circuitry. Yeah, probably north of $500, but I can't imagine it being closer to $1000 :/
That extra circuitry is like a dollar retail. That should not be a significant impact on the price. For the battery itself, three 18650s would add $5 to the BOM so I'm not expecting a huge difference from that either.
At the scale they have, prices probably not quite so low, but the power stuff would be more if they use higher quality parts and factor in the integration / firmware bits.