The problem with these sorts of comparisons is mixing tiers. Here one is mixing up entry level dirt bikes with a top tier road racing bicycle.
That $14 000 S-works is essentially the bicycle equivalent for MotoGP bikes. You can't get a pro level racing MotoGP bike for 14 grand. They're a bit more expensive than that.
Economics also doesn't work by adding in the prices of unprocessed raw materials and claiming that should be the value of a product. There's usually some manufacturing and design involved as well. Also calling CF "plastic" or tires "rubber" is such a gross oversimplification. And also incredibly inaccurate and false as well.
As to whether any regular old consumer actually needs a top tier road racing bicycle, MotoGP bike or a formula one car? Well if you can afford it and want it...