Michigan CG,
My post had to do with the concept of the contributory value of a feature within its market. I don't believe I said it did not have contributory value due to lack of sales, hence my use of the terms "if" "may" and "may not" in my post. To expand then, and perhaps clarify, the following is from the Appraisal of Real Estate, which, coincidentally, uses a pool as an example and really, was the point of my post.
"The principal of contribution states that the value of a particular component is measured in terms of its contribution to the value of the whole property, or as the amount that its absence would detract from the value as a whole. The cost of an item does not necessarily equal its value. A swimming pool that costs $10,000 to install does not necessarily increase the value of a residental property by $10,000. Rather, the pool's dollar contribution to value is measured in terms of how valuable its benefit or utility is IN THE MARKET. Its contribution to value MAY BE lower or higher than its costs. "