Sa'id bin al-Musayyib (may Allah have mercy on him) used to say: The diyah (blood money) of a slave is in (the measure of) his price, just as the diyah of a free man is in his (fixed) blood money.
Ibn Shihab said: Some men used to say otherwise: he is only a commodity that is to be valued.
Hadith Referenceالسنن الكبرى للبيهقي / كتاب الديات / 16357