So cheap it's sad..........

At 400,000 miles/kilometers the engine is only one of the major concerns. The chassis has also had that many miles, which includes the transmission, differential, ALL suspension components, radiator, AC compressor, and so on. There are many many items that could be on their way to failing that could easily cost as much to deal with as an engine rebuild. A diesel engine is just one component of a complex system and even tho it may last a million miles, all of the stuff around it may may start to fail and eat a big hole in your wallet.