Cost may well be universal, but so may be the value placed on exploration. In fact, the history of life on Earth can be viewed as a history of exploration. I don’t think we actually have much choice but to explore. We are driven to do it. Cost is certainly a limiting factor, but there are always individuals willing to pay high prices to (for example) get to the top of Mt. Everest or reach the poles or walk on the moon. And they can generally find others willing to help them pay for the adventure. Space exploration is costly and dangerous, but so far we haven’t stopped doing it. If one nation does stop, there are others willing to step in and fill the gap. I don’t think we will ever completely call a halt, and if not then maybe through small, incremental steps we’ll get to a point where it doesn’t seem like such a big deal to finance a trip to the stars. I do agree cost is a factor, but it’s not the only one that will influence our decisions, and it may not be the biggest one, if and when we get to that point. At the same time, as I said before, I think interstellar travel is likely so difficult that it isn’t being done by anyone on any large scale. The “U” in “UFO” means “unidentified,” not “alien spaceship.” UFOs may be real phenomena, but once they become identified, it has always turned out they are of terrestrial origin, such as classified experimental high-altitude aircraft or oddball refraction of the light from celestial objects by the atmosphere.