How much does a cracked head cost to fix in a car?

Without knowing the make, model, and year, it is hard to say. The national average for a head gasket repair is $1144 to $1468. It's generally less than $100 in parts, and the rest is in labor. You can find estimate calculators online.

One example: http://repairpal.com/estimator/head-gasket-replacement-cost

There are also many others.