I dont know why you all freak out about this.
1. A big high-quality cloth is around 5-10$ in your local convenience store, so 19$ for Apple branded one is not outrages. Apple is also charging you a 29$ for a silicon iPhone case that probably costs only a few cents per unit to manufacture.
2. It will be a stupid move for Apple to add it for free in every MBP box, because most of these cloths will stay in the box and would be thrown in the trash eventually. Apple does not want to generate any unnecessary waste so including in the package anything that is not going to be used by vast majority of users is pointless and goes against their environmental policy.
3. Nobody cleans its brand new Mercedes with hands soap and old tshirt. You would probably invest a few hundred bugs for a professional cleaning kit. The same applies if you buy an expensive laptop. You would want to keep it pristine at least at the beginning.
4. If you spend 19$ for a cloth, you most likely take care of it, clean it and won't just throw it in the trash when it gets dirty. When you spend money on something, you will likely treat it differently compared to getting it for free. Again, less waste.
5. How much would have cost Apple to give a cloth for free? 1$ per MBP? If they sell 10 millions MBP, this means $10 million of extra cost. I would rather prefer Apple to donate this money or invest it in something more useful for its users.
6. We dont know the initial stock of cloths so if it is sold out, it may be the case that they had only a few thousand initially. It does not make sense for Apple to place a larger order from its suppliers for a new product they do not know how well it will sell.
7. We dont know if it is regular cloth with Apple logo on it, or it is some fancy high-tech fabric. These latter are usually a bit more expensive.
8. With the thin bezels on the new MBP it makes more sense than ever for Apple to offer a cleaning solution. You will probably wont believe the amount of people that destroy their displays by using different cleaning methods that destroy the coating or the display itself.