We have a subdivision which is entry level value homes. In the mid 90's, two to three builders were constructing in this development. All were what I'd call tract, production style and average to average plus quality. One builder utilized steel frame construction. He had a handful of floorplans, and set crews, so the idea was that the savings in waste and pre-engineered design would save money. All the steel 'benefits' were loudly touted by this builder.
The other two builders proceeded on with their frame homes as usual. Steel man had fiberglass tubs, vinyl flooring and laminate counter tops. The two frame builders used ceramic tile flooring, cultured marble tub surrounds, two tone stucco pop outs, raised entries, and overall had a product with better visual appeal. To this day, the market recognizes a slightly superior value in the frame homes with the decor upgrades.
Pam, George, and others have done a fine job explaining. The only thing I may add is an underline to what Greg Boyd and others have stated regarding buyer knowledge and the items for which they see more value. As others have stated, it is not the appraiser's place or call to assign value to items based on thier own personal opinions. We report the market reaction, we do not create it on our own.
In my sales experience, there are relatively few buyers who will listen intently
and understand all the new and improved features of a different construction material beyond a 2-3 minute sales speil. Most, sadly, have other things on thier minds, and a relatively short attention span for the boring nuts and bolts details. You'll gain the interest from an engineer or similar personality type. That person will go home and do his own research and have a list of pointed questions for your next meeting. He/she will be the most likely candidate for assigning value to such items and opting to pay more. The average Joe is mostly concerned with the payment fitting his budget, the wife being happy with the floorplan and decor items, and will the garage accommodate his SUV.