Quite a few, plus the assorted blinker circuits, external power supply, etc. I also used up a lot of Tamiya spray cans to paint the Aztec pattern on the hull. At $10 a can, that quickly mounts up. Another A$60 or so to order the NX-01 Aztec painting masks from CultTVMan. Also included is the cost of a few blind alleys - ideas that didn't pan out. Keep in mind that I didn't have so much as a soldering iron when I started, so a lot of basic equipment got rolled into the budget for "The NX-01 Project", which I won't have to buy again for the next model.
On the Refit, I'm already a couple of hundred dollars in the hole buying up components to experiment with infrared remote control, sound effects, etc. And half a dozen different spray can colors to find the right ones to paint the Refit Aztec, just to conclude that I'll probably need to bite the bullet, get an airbrush, and mix my own colors. A few dollars more for the airbrush ...
My point is that these things mount up pretty quickly, and so A$110 for the basic plastics is nothing compared to the final price you'll end up paying to build the obsession. Even if you have some of the above already lying around. But don't let that stop you ...