Broken keyboard: Apple store policy?
In a general sense, policy is how the employees handle your specific situation, but here is the legal description of what the hardware warranty policy is:

http://www.apple.com/legal/

As regards to any company, they may go above the policy when it's the commonplace or expected thing to do so it never hurts to ask nicely if some accommodation could be made in a specific case.



This line of thinking has helped me in the past. Think of a warranty as a guideline for who pays for a repair. Within a warranty (or AppleCare), it is Apple's responsibility to pay for most repairs except for intentional misuse or accident.

After the warranty period has passed, it's the consumer's responsibility to pay for most repairs except for the most unlikely event that there was a clear error on the manufacturer's part in making the product.

I have found Apple to be very understanding of honest mistakes when attempting a normal consumer activity (changing RAM, cleaning, etc..) and covering things that might be considered consumer damage.

In this case, you could ask Apple to cover your keyboard, but it seems you should instead ask for a repair quote and expect to pay for a repaired keyboard. I believe a USB keyboard replacement (entire new keyboard) is in the $29 dollar range but you could reach out to Apple and get a quote for your specific location and part number before deciding what to do.