How much should it cost to fix a Timing chain capfor 2004 volvo

I am not sure what you are asking because the 2004 XC70 has a 2.5L turbocharged engine which uses a Timing Belt not a chain. Replacement should be done around 100K miles and with costs and labor are around $1000 to replace it before it breaks. Are you asking about the Belt cover piece and or cap? That should not be expensive to swap out if it is cracked or broken labor wise, the cost will be in the part if you are buying a genuine Volvo part. Try to find a used part.