This set is very highly priced but I don't understand why people are trying to find an explanation for this price. A lot of things in our life cost much more than their value, often we pay more just for the brand (actually we pay more for Lego than for any other clone brand, and often the quality is basically the same). Marketing department decides what is the most suitable price for an object, they have the production cost and they decide the margin.
The brand Cat is surely an attractive factor, I'm sure lot of people will buy the first Lego Technic Cat model and will not care about the price.
The 18+ thing is only a box art style to help adults (not Afols) to identify products more suitable for them, it was explained when it was introduced.