Is it worth it for Apple to deny the industry a cutting edge database with the only cost being a single day's profits or less? Of course it is.
And you're spot on about the cost of development. I'd imagine 12 - 48 hours of profits from Apple would be enough to fund its database R&D for the next 10 years.
I'm sure a company that's richer than many countries is really, really concerned about the cost of development.
The benefit of making sure no-one else can benefit from the technology, on the other hand...