Just to comment a bit further... W/D value is very area dependent. It will not always translate into higher rent. Sometimes it will just mean lower vacancy. In a downturn, a better product will suffer less (has a second bathroom, in suite W/D). Vacancies are more concentrated on units without upgrades...but it is very, very relative to the area in town. A good location is worth inconvenience. This is why companies like Boardwalk, Westcorp, and Mainstreet have not shelled out millions to renovate their Edmonton buildings to have unit W/D. Many excellent locations and the ROI isn't there to install unit W/D.
A really solid understanding of market supply and demand is really key to answer this question, along with some understanding of market absorption. All this is to really pin down a dollar value for a W/D unit. As a GC you will know the cost side but a lot of retrofits don't actually pay off. The take out is a really critical part of the question as well.