About the term entire system, we mean the camera & included lens, extra lens, flash, tripod, filters, and the list goes on. And mind you, each single item you see cost quite a bit, the most expensive being the extra lens. Some professionals have got 10 lens or more and some of these lens cost many times more than the camera itself.
It's easy for you to say right now (because you don't own one) that you're not interested in going beyond the basic kit (camera body & lens), but after taking a few shows, you'll start wanting to be a little bit more creative and that's when the trouble starts. First a flash, then followed by 3 tripod (first one is cheap but breaks/wobbles, second one you double but after a while you think you need a ballhead or a panhead so you end up buy a manfrotto which cost you 1/3 what you paid for the 2nd hand camera) all because you want to capture the National Day fireworks. To take soft images for a friend's wedding, you buy a few filters, a reflector & a flash diffusor. But for the next project, you buy a wide angle lens that cost more than your tripod; but because the size of the lens not the same as your kit lens, you end up buying another set of filters.
Do you see where the story leads? This unfortunately isn't the end; it's actually just the begining. Cos after owning a few lens, you feel you've outgrown the D50, so you end up buying a D200 and then the cycle begins again, but just not as bad because you already have some stuff you can carry on using.
So there! I've given you your future (like many many others before you). And once you start to sum up all that you've spent, you'll realize that you could have actually bought a new HDB flat instead. hehehhe.