Ultramarine's price rivaled gold because of where it came from

The vivid blue pigment known as ultramarine was produced by grinding lapis lazuli, a semi-precious stone historically sourced almost exclusively from a remote mountain region in what is now Afghanistan, then shipped an enormous distance to European markets. This narrow, difficult supply chain made the pigment extraordinarily expensive, at times comparable in cost to gold by weight.

Because of this expense, Renaissance painters typically reserved ultramarine for their most important subjects, most famously the robes of the Virgin Mary, making its use a visible signal of a patron's wealth and the painting's spiritual importance rather than a purely artistic choice. Contracts between patrons and painters sometimes specified exactly how much ultramarine should be used, since it represented a real material cost that needed negotiating.

This history explains why certain shades of blue carry such strong associations with reverence and status in Western art — the association wasn't symbolic from the start, it was economic, and the symbolism grew up around the economics. A color's cultural meaning often started as a simple fact about how hard it was to obtain.