The real cost of supermarket bread

A £1.50 supermarket sliced loaf and a £4 artisan sourdough are not the same product, and they’re not eaten the same way. The supermarket loaf is roughly 400g, with about 320g of usable bread (the rest is end-crust waste and air); the artisan sourdough is typically 800g, with maybe 750g of usable bread because the crust is the point. So per-gram, you’re paying 0.47p vs 0.53p — within rounding.

Density matters more than weight. Sourdough is hydrated higher and the crumb is closed; one slice of sourdough holds together under a loaded sandwich where the supermarket equivalent collapses, so people eat fewer slices. Time-and-motion studies in school catering kitchens find that sourdough sandwiches use 14% less bread by weight per made sandwich.

Keeping qualities. The supermarket loaf is good for 36 hours and stale within a week. A real sourdough is at peak texture two days after baking and still very good five days in (especially toasted). When you factor in the loaves people throw away — the WRAP figures put household bread waste at 15.5% — the actual cost-per-eaten-slice gap narrows again.

The headline that £4 bread is "expensive" comes from comparing the headline price, not the bread you ate. Once you do the maths, the gap is closer to 12%, and you’re also buying something that doesn’t need a 36-ingredient label.