Generally speaking? I disagree. Generally speaking, given a line that makes big profit, and a line that makes small profit, all effort to the big profit line g

Generally speaking? I disagree. Generally speaking, given a line that makes big profit, and a line that makes small profit, all effort to the big profit line gives the greatest overall profit. What you have presented is not general; you've presented a series of special cases where it might be a good idea to keep the less profitable line running too. There are many such special cases, but in general, if your options are a line that makes big profits and a line that makes small profits, you'll be most profitable by picking the former.