How Much would it cost to have a bent axle replaced?

They are separate axle assemblies, right and left, from the differential. Unless both are bent, only one will need to be replaced. You have the option of an after-market (non-OEM) part that is just as good - Can poss. save you about $300! The cost, parts and service can be around $400-800. It just depends on how many parts you need. You will not know that until you pull it apart and inspect the damage