Robots make for great expedition R&D. They can gather a lot of information very cheaply compared to manned spaceflight.
I'm not sure space travel has to be profitable. Certainly Christopher Columbus's voyage was not considered (by most people at the time) to be profitable. Yet economies of scale could definitely be taken into account. It is often said that the computing power of the Apollo missions to the moon were less than that of a TI calculator. It seems we should be able to have unmanned missions to the moon by private sector or even partially public funded. After all were sending DIY cameras into near space.
Of course they don't necessarily have to be profitable. The Chinese continued their expeditions for 30 years without being "profitable". My point is that if you want a sustained program that will grow, being self sustaining would be necessary. Eventually it has to pay for itself. I don't think the Europeans would have continued their expeditions if all the returns they got were 100 years of financial losses.
I'm not sure space travel has to be profitable. Certainly Christopher Columbus's voyage was not considered (by most people at the time) to be profitable. Yet economies of scale could definitely be taken into account. It is often said that the computing power of the Apollo missions to the moon were less than that of a TI calculator. It seems we should be able to have unmanned missions to the moon by private sector or even partially public funded. After all were sending DIY cameras into near space.