Face it, at that price it's pretty clear what it means. It takes about 100 standard 18650 cells to make a kWh. That's about $3.50 a cell. So a typical ebike battery pack, with 40 cells, has $140 worth of cells in it, at that price. Musk believes battery prices will start to drop noticeably when his Reno facility comes online.
It's just a matter of time. An ebike battery pack, and a good one, for $200. Motors don't cost that much. Everything else is a pretty nice bike you can buy online for $400.
There's a man on Endless Sphere selling a really clever spot welder for $150. That's what you need if you want to make your own packs, and want to do it the best way.