Have you ever asked yourself what is the most expensive part inside your Rolex ? Taking into consideration that almost all movement parts are essential (except for a screw or two), it would be unfair to single out any particular bit. However, for the sake of simplicity, let's assume that all parts are equally important and from that, the most expensive part would be the one with the best dollar/weight ratio.
The escape wheel is the last and the lightest wheel in watch train and one of the 3 vital parts responsible for timekeeping and accuracy. Together with pallets and the balance wheel, it is really the 'heart' of the watch mechanism - a 'device' that makes your Rolex tick & tock.
The photo below shows the escape wheel from Rolex calibre 3135 placed on digital scale.
The weight of the wheel is 0.006 gram. In other words, the total of 167 wheels would have a combined weight of 1 gram. With a price of US$ 28 per wheel, 1 gram of escape wheels is worth US$ 4,676.00 !
Do you know of any other machine made and mass-produced piece of metal worth 4,6 million US dollars per kilogram? That's why the Swiss don't bother about making hammers and screwdrivers. If they did, you'd have to be Warren Buffet to take up carpentry as a hobby.