You have just been offered a salary of £48,000. A win, or a letdown? It depends entirely on what you measure it against. Drag the marker, or tap a comparison, and watch the offer stay exactly the same.
The offer never moved. It was £48,000 the whole time. All that changed was the number you set beside it, the reference point. The same salary went from a raise worth celebrating to a broken promise, and back.
This is why "was £1,000, now £900" beats a plain "£900". The crossed-out price installs a reference that turns the identical amount into a gain. Setting the reference point is the sturdiest, most usable lever in Prospect Theory (Kahneman and Tversky, 1979), and unlike its famous cousin loss aversion, it is not the part the science is still arguing about.