This meme comes from people who've watched too many bad sci-fi shows and don't have a good grasp of history. The people going to space will be the intersection of those who can afford it and those who want and are capable of going. The first people who traveled the oceans were not the lower class. They were the upper class who could afford to fund or pay for the journey by pooling money or independently pay for it.
The poor you refer to didn't come until much later in the age of discovery.
Is it gonna be disposable lower-class people?
In age of doscovery shipowners and governments assumed a 50% death rate from scurvy for their sailors on a major voyage.
TThe past is fireign land, executions were a public holiday and children came to watch. We used to gove cocaine to children to stop them crying.