Not sure where you're looking but modulars are definitely cheaper in the Western US. Many off the freeway modular dealers can get you a three bed for under 200k. They are not attractive though. Clayton, Champion, Commodore , etc fall into this category.

If you step up to a higher end manufacturer you end up paying about the price of a site built but with much nicer finishes than the comparable site built. Method, Ideabox, Timberland, etc fall into this category.