In a world of complexity it is nice, from time to time, to get back to basics. Simple floor designs are not only the least expensive to build, but also the easiest in which to live. Form is great, but form can lose its luster over time and give way to functionality. Because of that, the simple home is here to stay.
Simple Need Not Be Plain
Just because something is simple (for example straight walls, square rooms), it does not follow that it has to be plain. Over my 20 years I have learned a great deal about how to take a flat wall and get really creative. While I do that, I keep in mind the expense. An example of this is the dutch gable. I keep this in mind anytime I'm dealing with a smaller simpler home. It's easy to build, costs little more than a standard gable, and in many cases is very attractive, giving the home a totally different feel.
Though cost may be affected more by the exterior of the home, long term livability is affected by the interior. Space saving is the key to keeping costs down. I look for every square inch I can squeeze out of a home's interior. This may affect the "simplicity" of the interior and make it seem more complex on paper, but in reality, it actually makes more sense. Examples include making hallways as short as possible. I look for storage anywhere I can, and a good deal of the time I find it at the end of a hallway. Storage makes your life simpler, and it make the home worth more for you and if you ever decide to sell.
Simplicity on the exterior while still being creative with "curb appeal" and keeping cost down is what I strive to do on every plan. At the same time I work to find space in the interior to increase functionality and livability which increases the value without significantly increasing cost.