What moves the number
Fibre first: silk and silk blends cost more than wool because the process is slower and the risk higher. Knot density second, because a finely knotted rug holds more water and takes longer at every stage. Condition third: unstable dyes, a fragile foundation or existing damage all require slower handling. Contamination is quoted separately because pet urine requires full immersion and flushing rather than a standard wash, and that is genuinely different work.