Update handbook average/recommended pricing for keyboard and mouse

Updates the mouse and keyboard average/recommended pricing to reflect the pricing of an apple keyboard and trackpad so people are able to replicate the same interaction experience as an apple laptop gives (this is often desired for better posture at home or remote in combination with a latop stand or external monitor).

This includes the pricing difference when looking at the EU apple shop vs the US apple shop (pricing in the EU is often more expensive due to the mandated two year warranty instead of one year)

Related slack discussion can be found at https://gitlab.slack.com/archives/C0SNC8F2N/p1558986955048000