A solid gold bracelet bought twenty years ago is still worth real money today. A gold-plated one from the same year is worth almost nothing. Same look, on day one. Completely different outcome. The reason comes down to what each piece is actually made of.
Value lives in the metal, not the surface
Gold is scarce, it does not rust or corrode, and it has been treated as money by nearly every civilisation for thousands of years. That shared, global agreement that gold is valuable is what puts a floor under it. When you own solid gold, you own a piece of that floor. A plated item only wears gold on the outside; underneath is cheap base metal, so there is no floor to catch it.
Why plated fades to nothing
The thin gold layer on plated jewellery is measured in microns. Daily wear, skin, water, and time rub it away, exposing the metal beneath. Once the surface goes, so does the last of its resale value. There was never enough gold there to be worth melting or reselling in the first place.
Why solid gold keeps a floor
Solid gold can never be worth less than the gold it contains. Styles change, but the metal does not, and it can always be sold or melted back to its value. That is the difference between a fashion product, which is designed to be replaced, and an asset, which is designed to be kept.
Real gold does not fade. Real gold is still real gold twenty years from now.
It is worth remembering that gold's price still moves up and down over time, so its value is not fixed. But it will always be worth something real, which is more than plated jewellery can ever promise. That floor is the whole reason we make solid gold and price it by the gram.