I charge the same rate for software development as I do for making graphite etchings on paper in aesthetically pleasing patterns. Consulting clients buy both of these things from me, in isolation or combination, on a regular basis. So if that's the way you're asking the question, "Yes, I could."
If the question is "If you brought nothing to the table other than the ability to write Ruby code, would you be able to charge $YOUR_RATE for writing Ruby code?", I think I'll go with "I can guarantee you that someone gets that much for writing Ruby, and probably more besides, but it probably wouldn't be me" and "Wait wait wait, you seem to want to sell yourself as a commodity coder, don't sell yourself as a commodity coder, down that path lines madness."