My point of view is that they are missing the whole concept. To me, prefab, is an option to been able to obtain a very nice and modern design with some off the shelf components and the main parts being done in a factory-type fashion.
So, what are you going to get? a nice modern design, green construction, lot of glass, hardwood floors (or bamboo but having now hardwood, I rather have concrete instead) and a great open layout/kitchen with all the ammenities. All this without having to hire a great designer/arquitech... so far so good.... but when you have to spend between $260,000 and $650,000 (with some cases of almost $1M!!!) and having to deal with foundation and city permits... I think is better to hire a new, fresh from school arquitech, have some input on the design and even, maybe, pay less..... It's like the knife industry. You can get a very nice custom, totally handmade knife for you only for $500 or pay $950 for a big name's midtech (midtech is a factory made components that are finalized and finished up by hand...) Sorry, I don't get it.
When the prefab starts around $80,000 - $150,000, let me know and I will buy a piece of land to built.

(photos and info from www.fabprefab.com.