What the “Apply variation costs by default” setting is
If you have explored the settings page, you may have found a setting named “Apply variation costs by default” with a short explanation to the right of the checkbox. Here, we will dive in to what this actually means.
Here is the Tl;dr – If you are using this new setting, variations with blank Cost of Goods will now automatically apply the default cost ONCE you have gone into the parent variable product and hit “Update” — no further action needed. If you need a $0.00 Cost of Good variation, use the new “Use $0.00” checkbox on that variation.
First, know that this setting only applies to Variable products and the child Variations created from these products. When creating a Variable product (see here for details) you can set a Default Cost of Goods to pass to the variations. Initially, after installing this plugin, you must specify which variations are going to use the default. This is how the plugin was originally designed, but we have since made the change to allow the default to be applied without user interaction. This setting is what makes that change.
If you do not activate this setting, nothing in your store will change.
If you decide to activate this setting, all the blank Cost of Goods fields in variations will now apply the default. NOTE** You must save the parent Variable product to get the variations to save the default cost correctly.
In order to preserve the ability to set a $0.00 Cost of Goods on variations, once the setting is activated you will notice a new checkbox next to the “use default” checkbox, labeled “Use $0.00”. You can only use one of the two checkboxes, and selecting one will disable the other.