Was a biopsy necessary given no evidence of cancer, tumors or other irregularities? Hard to imagine it being necessary, and I personally wouldn't have had it done. But my philosophy (and it's served me well) is never have allopathic doctors do what isn't absolutely necessary - in your opinion in addition to theirs.
Colon cancer is slow moving and with no evidence of it, I would definitely end the billing and procedures right there. But maybe the doctor thought you needed the extra reassurance?