Airplanes are expensive vehicles. There are certain reasons for this. Safety comes first. Back-up/spare systems, advanced electronics, lightweight and durable materials increase the cost. Some parts of the planes are much more expensive than the others. The most expensive parts are of course the engines.
The most important reason why engines are expensive is that they have to work under extreme conditions. High pressure, high temperature and very high rpm (rotation per minute). There have to be critical parts that have to withstand all of these conditions at once. Perhaps the most important of these parts is high pressure turbine blades. These little blades must be able to withstand the heat generated by the burned fuel at a thousand degrees, while facing extreme forces and spinning with thousands of revolutions. When the heat is so high, they must be cooled. But how?
Instead of being made of each blade-filled material, they are designed with empty air ducts inside. The detail of these holes are clearly seen in the picture. The cold air of the engine that is not yet burned is used to cool the parts after the combustion. The air inside engine is actually hot almost everywhere, but unburnt air is much cooler than burnt air-fuel mixture. For this reason, they are produced from a very very special material, again under very special conditions, with a 0-tolerance margin. It is not surprising why these parts become very expensive after the hollowing out of a piece that has to withstand such harsh conditions.
There are 80-100 of these blades in each aircraft engine. Their weight varies between 25-30 gr. The prices are around 800-1000 USD with today’s figures. We are talking about 80-100 thousand USD for a set of blades. It is possible to buy pure gold of the same weight at this price. In other words, each blade has a cost equal to its own weight of pure gold. The engine contains many similar parts and these parts are replaced with new ones every 4-6 years. Therefore, the maintenance cost of a single engine increases to 3-5 million dollars.
If you hear from an aviation engineer that the engines are as precious as gold, or that the engines are kept as sensitive as gold, you know why. Look at the engines once again with this aspect on your next flight!