Amr bin Shu'ayb (may Allah have mercy on him) said: The Prophet (peace and blessings be upon him) used to value the camels for the town-dwellers at 400 dinars or its equivalent in silver, and he would apportion it according to the prices of camels; if camels became expensive he would raise the value, and if they became cheap he would lower the value accordingly.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16166