I had a similar issue with my car: a small part broke and the supplier said that a spare part was not available. However, they could supply an entire unit (essentially most of the cooling system). The result was that a part worth a few dollars cost more than $1000.

 

The explanation was that it isn't worthwhile maintaining stock of all the numerous spare parts that might be required, so they just replace whole chunks. Better for them, not so good for the consumer.