We find affordable alternatives for a living, so treat the following with appropriate scepticism — and note that we have tried to be straight about where the answer is no.
For scale: across the 44 looks in our own pricing study, the median saving was 83% — and the category where the gap closed hardest was shoes, which is exactly where the answer below is most often no.
When it is genuinely worth it
When the price is mostly brand. Some categories carry a very large margin between what a garment costs to make and what it sells for. A plain cotton t-shirt, a simple slip skirt, a basic knit — the construction is not complicated and a well-made cheaper version really is comparable.
When the shape is the appeal. If what you like is the silhouette — a wide-leg trouser, a square neckline, a particular length — that is a pattern, and patterns are widely available. You will find it.
When it is a trend you are unsure about. Testing a shape or colour at a lower price before committing is straightforward good sense. If it turns out not to suit you, you have learned something cheaply.
When it is occasion wear. Something worn once or twice a year is where the arithmetic most favours spending less. The fabrics that read as expensive on an evening — satin, velvet, sequin — are not expensive in themselves.
When the colour matters more than the label. A garment in a shade that genuinely suits you, at a lower price, will get worn more than a costlier one in a shade that does not.
Three times it is not
1. Structured outerwear and tailoring. A coat or a blazer is doing structural work — interfacing, canvas, lining, the way a shoulder is built. That work is expensive and it is exactly what gets removed at a lower price. The cheaper coat usually looks similar in a photograph and different on a person, and it will not last. How a coat should fit covers what to check.
2. Anything where the fabric is the point. If the appeal is a heavy silk, a dense cashmere or a good leather, the fibre is most of the cost. A version at a third of the price is a different fabric, and it will behave differently from the first wear. What makes a knit good quality covers how to tell.
3. Shoes you will walk in. Construction, footbed and sole quality decide comfort over a full day, and none of them photograph. A cheaper heel for an evening is fine; a cheaper everyday boot is often a false economy. Buying shoes online covers the rest.
The trap that undoes all of it
A cheaper garment you would not otherwise have bought is not a saving. It is a purchase.
The arithmetic only works when the alternative was buying the expensive version, not when the alternative was buying nothing. This is worth being honest with yourself about, and it is where most of the money actually goes.
Cost per wear covers doing the sums honestly.
A reasonable rule
Spend on the things doing structural work and worn constantly — outerwear, everyday shoes, tailoring, the bag you carry daily.
Save on the things where the shape is the appeal, the fabric is simple, or the wear count is low.
That division holds up better than any rule about brands.
If you want to find the alternative rather than hunt for it, DUPI reads an item from a photograph and searches real UK shops, with real prices and links, and reads each find against your colours. The dupe library has finds already put together this way.