We call a "paper" a "paper" because it is written on paper. In this blog we've been examining some metaphors for writing, but this is a classic metonymy, like a "glass" of water. Container for the thing contained? Not quite, more like "writing surface for the thing written on it." The same way we might call a painting a "canvas" when what is important is not the canvas but the paint.
If you use better pens and inks, then you will find the need to use better paper as well, because fountain pen ink doesn't tend to do well with the cheap stuff. I just got a nice Clairefontaine notebook when I was in New York. I like Rhodia pads for the paper, but don't like their vertical orientation very much. Some go for Moleskin, but I don't find it great for fountain pens because it doesn't want to absorb any ink.
Much like fountain pens, even if they cost 75 bucks, get to be cheaper than bics that are rapidly thrown out or lost, good paper will tend to last longer: you will use it more economically in the long run, find more specialized and creative uses for them. I use cheap pads too, mind you. In fact, if is not a Rhodia pad or Clairefontaine, it should be as cheap as possible. With so much information exchanged electronically, we will have "papers" published on line that will have never been "papers" in the literal (or metonymic) sense at any stage of their production. At some point paper itself will only have a raison d'être as a craft or luxury item. The fountain pen may well outlast the bic.