I think that doesn't speak to the expansiveness of Apple's response. It's my understanding that the burden to undertake this effort being excessive is only one

I think that doesn't speak to the expansiveness of Apple's response. It's my understanding that the burden to undertake this effort being excessive is only one of their grounds for argument. They are additionally arguing that it violates free speech principles, and also that the request goes beyond their initial compliance efforts to aid in the investigation to fringing on violating Fifth Amendment principles by asking them to go above and beyond the simple compliance. To my untrained eyes, they're basically saying that instead of having a key and being asked to turn over the key, and doing so - they're being asked to devote efforts to create an entirely new key that would unlock many or all doors. Which could then be used in many other unrelated "need to open the door" situations.