So this is an example of the Cursed property being used. For you to craft something like this, it wouldn’t make sense for it to be a less in cost.
And then you can look at this item that someone made and see how a cursed item can be a very powerful tool to have:
There wouldn’t be an easy calculation to auto assign a subtracting of WL for an item b/c of the many variables that there are for a negative effect. That’s why the Special property goes through the questions it does in Chapter 9 to help you refine and figure out the cost of that Special Feature.