Does Droskar's Guiding Ring stack with other crafting cost reductions?

[Katydid]

Inner Sea Gods - Droskar's Guiding Ring wrote:

Once per day, the wearer may use charm person. If Droskar is the wearer’s patron deity, any time the wearer crafts a magic item, she may choose to pay half of the item’s construction cost instead of the full cost. The wearer spends time working on the item normally, but at the time of completion there is a 50% chance that the item turns out nonmagical and worthless.

So if I had, say, Hedge Magician (-5%), Requires Skill to Use (-10%), and Requires Specific Class/Alignment (-30% price = -15% cost) could I attempt to craft at 20% cost with a 1/2 chance of failure?

[Helcack]

I don't believe so because it's specifying that you pay 1/2 the items construction cost instead of the full cost and it's an ability so I don't know if it would be modified. If it was though then it would be original cost -35% then construction cost-50% then-5% off that because each modifies a different cost.