The anode cost $45 and it took around 30 minutes to replace. The one I removed was almost completely destroyed, so I was lucky.
Should you think of replacing your sacrificial anode in your heater, it is a relatively simple job and well worth doing.
Here is a YouTube video of how to replace your sacrificial anode.
Warning; you should check that where your heater is, it has sufficient room above the top where the new anode will be fitted. Often the anode is longer than the ceiling space above the heater.
On this heater, the top cage has to be removed to fit the new anode.