It's most likely similar to the PS3 launch situation - they had two models, a $500 20GB system and a $600 60GB deluxe system. They only really made the $500 system so they could advertise a cheaper price, and then they released it in such tiny numbers compared to the $600 model it shouldn't have even counted as a launch. Then they discontinued it as soon as possible, because they lost a lot more money on the $500 model than the $600 model (at the time they announced the discontinuation reason as because the $600 one was more popular, which was accurate because the $500 version couldn't be found in stores so people bought the pricier one instead).
Sony doesn't really want to sell the headset-only package, they only announced it so they could market the PSVR as a $400 device rather than a $500 device. The camera, two moves, and game collection definitely don't cost Sony $100 to manufacture/package, so that extra $100 gives them a lot more money per unit sold.