Are you sure the Concept II actually has a power meter?
Based on the product literature I think they're calculating power from a resistance curve. Similar to a fluid trainer. That approach works great indoors when conditions are controlled. And its completely and utterly useless on the road.
A cycling power meter is expensive because strain gauge installation is challenging and labor intensive. There's a ton of calibration factors that need to be include. The strain gauge itself is dirt cheap, getting reliable data from one is an engineering project.