To build a folly is essentially to do something a second time, something at an inopportune moment. That something is always the memory of something forgotten, about which we can paradoxically say "There it is again."
Follies were misunderstood, purposeless constructions. They were often only small, extravagant gestures in a garden, easily whisking off the imagination to distant lands, a sort of time capsule built to awaken the memory and induce surprise in passers-by. They marked locations, organized secondary paths in a park, or simply predicted the arrival of better times—a demarcation, a sacred spot, a mysterious trail, a hill whose tragic rocky nature begged for a tower, a party, or the arrival of summer.
“It is demonstrably true that things cannot be other than as they are. For, everything having been made for a purpose, everything is necessarily for the best purpose.” — Professor Pangloss
The bottom line is certainly of concern, both to those seeking profit and to those seeking value, but neither of these can be measured solely by the amount of dollars spent on production or product. The nonquantitative word "quality" conveys countless ways in which a more expensive thing might be more profitable and yet a better buy as well. The advantages of thicker metal in an automobile body can clearly be argued from various points of view, including resistance to denting and even simple snob appeal. Whereas the manufacturer can use these as selling points and also as justification for a higher price tag, the buyer can easily justify spending more for a car that will keep its appearance longer and provide a status symbol.