The pistons and cylinder heads on a diesel engine will be much more ruggedly constructed than those in a gasoline engine. You may be aware that GM tried to convert smallblock V8 gasoline engines to diesel with mediocre results (to say the least). Injectors? Most (possible ALL) diesel engines use a "direct injection" system, where fuel is sprayed directly into the combustion chamber just as the piston is nearing top dead center. As you may imagine, the pressure required to spray the fuel in opposition to the cylinder pressure is quite high (800 psi or so), so the injectors and injector lines need to be of high quality and rugged construction. Gasoline engines usually use a port injection system which will usually spray into an ambient pressure equal to atmosphere or lower(vacuum). The pressures found in those injectors and line will be no more than 90psi and usually alot less, depending on engine loading and speed. Many diesel powered vehicles will have what is called a "transfer" or "lift" pump that brings the fuel from the tank thru marine grade rubber lines, at a low pressure,to the injector pump on or near the engine. As I've already mentioned, the injector pump will usually be capable of 800 psi or so. The injector pump is among the most expensive components on a diesel (running into thousands of dollars), owing to the fact that it is not only rugged, but it also controls fuel metering and ignition timing via the timing of the fuel spray. I already mentioned that the lines from the injector pump to the injectors are of high quality and a high price to match. Gasoline (fuel injected)powered vehicles usually have one, relatively inexpensive electric fuel pump in the fuel tank. The lines are steel/rubber and should be able to withstand 100 psi. It's safe to say, without a parts book in front of me, that the engine and fuel components on a diesel that you've asked about are between two and three times the price of their equivalent on a gasoline engine, and a gasoline engine has no injector pump. Scared yet?