Oh yeah, you know those plastic interior clips everyone breaks when pulling off plastic panels? There are tons of models of them online and it's easy to print a dozen of them and keep them in a toolbox.
ABS plastic costs about $35/kg, so you can imagine the cost savings on just two Honda bumper clips.
As for precision, I remember someone building a click pen a while back. They took the ink cartridge and spring from another pen, and it worked. I don't know for how long, but with ABS, things last a really long time.
One of the first things I'm going to do with my printer is make some smaller pulleys for the x and y axis, right now I have 36-tooth pulleys on, and it hurts my resolution pretty significantly, but with a trade-off for speed. I could just go to 400 step motors (.9deg steps) without sacrificing speed, but I think I'll stick with the motors I have now for a while. I want to finish the engagement ring first, or at least try it.
In a couple weeks, once I'm done moving in, I'll put some of the printed parts up in the FS forum if anyone wants to build their own printer.