You might imagine that nobody needs to be persuaded of the virtues of good design. If a building – a school or hospital, say – is well designed, then surely it is better suited to its purpose? If an object – a chair or toaster, perhaps – is well designed, then it will be more comfortable, or won’t burn the thick slices? If only our perception of what design is, and what makes it good or bad, were that simple.

Take the Scottish Parliament building, designed by the late Enric Miralles after an exhaustive international competition process. Not only did he win the competition, not only did he design the building, but after its posthumous and controversially expensive completion it won all kinds of awards, including Britain’s top architecture accolade, the 2005 Stirling Prize. Not long after, a 12-foot long timber beam fell from the roof of the debating chamber, fortunately causing no injuries but forcing the place to close for several weeks. The beam incident joined a catalogue of other reported problems from leaking roofs to jamming lifts. But set those aside for a moment, on the grounds that all great public buildings have their teething pains. Instead, consider the vexed question of value for money.

If the Scottish Parliament building was a good design when it won the competition and was optimistically costed at £40m, had it ceased to be a good design when – much expanded and amended – it finally hit £430m? If so, then at what point along the graph did rising cost cancel out design excellence? In other words, is value for  money an aspect of design every bit as important as functionalism and beauty? Or is it merely a temporary – and perhaps misleading – overlay?

An earlier building whose troubled construction history closely parallels that of the Scottish Parliament is the Sydney Opera House. Building it was a protracted nightmare made worse by malign political interference. Its costs also rose tenfold. Where the Scottish building’s architect died midway, the Australian equivalent – Danish architect Jorn Utzon – was forced to resign. Functionally speaking, the resulting building was pretty poor. A world-class opera house it most certainly was not. But today, who cares? Utzon’s opera house became a symbol of Australia. It is the most famous modern building in the world.

So: was it value for money? Not in 1974, perhaps, when it finally opened, having been first designed in 1956. But since then it has steadily become better and better value for money.

Ah, you may say, but how many such works of flawed genius are out there, places whose design quirks and cost overruns we are prepared to forgive on the grounds of their beauty and impact or rare utility? More than you might imagine.

In Milwaukee, a post-industrial city near Chicago on Lake Michigan, the cost of the new Quadracci Pavilion – an extension to the city’s Art Museum – rose from $40m to nearer $120m as the extraordinary ambition of its architect Santiago Calatrava became apparent. The fundraisers had to return to their benefactors over and over.

They coughed up without demur, bewitched by the audacity of the design. The rising cost turned out to be no scandal. The bony, organically sculptural building duly opened in 2001. And now the crowds gather everyday to see it.“ The most extraordinary thing about the building,” as one university professor told me, “Is simply that it is in Milwaukee at all.”