Ideally, buying designer clothes should be about design.

Runway shows have a perennial fascination because they showcase (in rapid, often dazzling procession) a series of unique and original designs. They are a flick-book approach to art – glimpses into the mind of a designer with one theme, and perhaps hundreds of preoccupations.

The best designer stores, equally, are fascinating. Glancing through rails, even just taking in the mannequins and their lighting, pose, dress, can be an aesthetic pleasure, akin to any exhibition of design. One walks out the best of them feeling inspired (even if you couldn’t afford anything inside).

But many designer purchases are about three values, only one of which is design. Those other two values are branding and quality.

When making such a purchase, bear in mind which of those three values you are prioritising and why. This will help you decide whether to opt for that designer bag or its high-street equivalent.

Branding
The first value, branding, can be dealt with most easily. Everyone succumbs to it to a greater or lesser extent – the desire to belong to that view of life, that aesthetic, to buy into it and possess a part of it. While this is objectively the least rational value, it would be churlish to condemn it. And without it life would be a little duller. Buy into it if you want, but be conscious what you are doing.

Quality
Buying something for the quality of its workmanship is far more rational. It will last longer, and look smarter for a greater proportion of that time. In the case of classic men’s clothes such as suits and shoes, that quality will mean something lasts for a decade rather than a year.

Designer clothes will be better made than high-street ones. But the difference may not be as large as you think. Many suits, for instance, are made in the same factories for different brands – one buyer told me that Austin Reed, Aquascutum and Gieves & Hawkes suits are all made in the same factory despite representing high street, designer and tailoring in many people’s minds.

Some of those suits are only super 100s or below, and fused rather than canvassed. Designer doesn’t necessarily mean quality. Research the brand and know what you are buying if you want quality – Mulberry bags, for instance, are designer and they are still made in England and will last a lifetime.

Design
Design has value when it’s unique. So buy designer clothes for their design when you can’t find them anywhere else. As with much in this posting, this has an echo in Winston Chesterfield’s thoughts last week – I would pick out his sunglasses example as something that can easily be copied, and so found on the high street. Buying a designer version seems pointless. You are not buying it for design or for quality. It’s all about value number three: branding.

Other examples of pieces that can easily be copied are belts, hats, ties and socks. You may buy a designer version of this for its superior quality, but not for its design. The pieces that are worth buying for their unique design are those that are complicated: suits, dresses, jackets, shoes. They are unlikely to be copied well.

So, in answer to the question of whether to buy high-street or designer clothes, I say: analyse where the value is. Is it in design, in quality or just in branding? Thinking through those three should make the decision easy.