Maybe you don't live in a city with a big bike theft problem? Here in DC, where I live, there are kids who wander around with bolt cutters lifting bikes from bike racks, and at least in my experience, they're just as likely to go for a cheap bike as an expensive one, so you pretty much have to have a bolt-cutter-proof lock, regardless of your bike, if you don't want to get it stolen, which means a tempered steel U lock. I've never seen one of those for $10. It's especially frustrating because while the old rule of thumb was that you should spend 10% of the value of the bike on a lock, there's a floor of about $30, at least here, because of how easy it is to defeat cheap locks, which means you end up way over-spending on locks if you ride a cheap bike.

The goal here, as I understand it, is to make the bikes so cheap that there's no resale market for either the bikes or the parts, which might mean a "keeps honest men honest" $10 lock would be good enough.