Sure I do. I've been a professional programmer for almost 20 years. I have a pretty good idea about what sorts of things are hard to do and what sorts of things are easy to do. The FBI's requests are very easy. 50M is ~200 man years of work. That number is insane.
Have you ever worked some place that requires a security clearance?
Well, for Apple to develop this software, they would insist on it being developed in a locked down facility that doesn't currently exist (what Apple has is in use). I think they have said it's only about $100,000 of developer time (so maybe 2-3 months of work), but the infrastructure that would be necessary for the work to be done in a way that doesn't risk any leaks is expensive.
