That's not necessarily true. Most carbon frames are expensive because they are high-end models, not because of the material itself.

I would be worried about durability though, if this is used like other commuter bikes. Carbon frames usually come warnings to not lean them against sharp objects, not sit on the top tube, etc. Unlike metals, the fibers are only strong in one direction. Anyone bumping into this bike by accident, e.g. when locking it against the same rack, might cause damage to the frame.