Yep, learning curves can be expensive but they're also fun. It's all about priorities. I drive a very modest car, for instance, because there are so many other things that give me far greater pleasure.
The Oil Base FC draws a bit colder than the graphite, I guess because it is more black, but also more matt, so you don't get the shine of graphite. They're not as soft as graphite so I'm sure how well they would draw on smooth surfaces. Here is a portrait I did using them on a pretty toothy local paper.