many line of business applications have a need for the occasional "walk on the analytic wild-side"....another example, just because 1 chart in an application needs to calculate slope, doesn't mean shelling out major bucks for a stats package. It makes more sense to invest a few more hours (or a day or two) of development instead of product purchase overkill.

Sure- just because you "consider" something doesn't mean it becomes the only option. Sometimes what you say will be true. Other times the stats package would make more sense. Other times the customer might be better off with a different database that includes MEDIAN in its SQL so you don't have to roll your own.