Spices were so expensive in Western Europe primarily due to the immense distances they had to travel from their origins in Asia, involving complex and costly trade routes with many intermediaries. The transportation of spices by dangerous overland and sea routes, combined with taxes, tolls, protection, and insurance costs, greatly increased their prices—often 10 to 100 times higher than their cost at the source. Additionally, spices were considered luxury items, highly demanded by the wealthy and often used as symbols of social status, further driving their high value. This exclusivity and riskiness of trade made the spice market very profitable but kept prices high for consumers in Western Europe.
Economically, the supply side alone did not justify the high prices; there was a strong consumer demand in late-medieval Europe for spices both as food flavoring and, historically, as preservatives or medicinal ingredients. The role of monopolies by Italian, Portuguese, and later Dutch traders who controlled access to spices also contributed to maintaining high prices in the European markets.
In summary, the high expense of spices in Western Europe was due to the long, complex supply chains with many intermediaries, high transaction costs including taxes and protections, strong demand from the elite as luxury products, and monopolistic trade control by Europeans themselves.