A condo that consists of just one or two high-rise towers can look imposing, while a low-rise development with a handful of blocks can feel charming. But this introduces complications that buyers may overlook. An issue is the subject of substitution within the same development. Case in point: there’s a certain new launch project in the Great World area that entered the market in recent months. The starting price for units was around $2,877 psf, which is very competitive for a location with such strong attributes. But once you get up to the units in the higher floors, prices start to exceed $3,300 psf. It is not unusual to see prices increase the higher it is located, but in this case, the increase is more than gradual. Let’s say as a buyer, you find a $1.86 million unit, a two-bedder, that perfectly fits your budget. But then, because of bad luck or hesitancy, the units on the ideal floor are sold....