They are virtually impossible to get a loan for and all the expense in a house is in the interior which as per above isn't included, so whatever they are advertised for - double it and then some, unless you have some really good contacts in the building industry or you are a tradie yourself.

We are building a transportable/relocatable (which are harder to get loans for too, but not impossible) and I lost count of the number of times we heard "its not a kit home is it? We don't give loans for kit homes".