First of all, I believe that [the dream of] just making a colony on Mars, per se, is obviously pointless, and actually wasteful. Per se, a small research station would be much better, and could be productive from a global utilitarian perspective.

However, things change when speaking of an economically self-sustaining base; and eventually a base theoretically capable of full-self sustenance (not dying in case there was a transport disruption or Earth itself suffered a disaster). This simplifies the funding discussion to start up costs and r.o.i.

In that case, humanitarian-utilitarian arguments such as expanding the Human civilization to other planets (Musk's call for making life multiplanetary), backing up life, etc. also start making a little more sense (if the colony isn't self-sustaining all of those points are moot).

Is that feasible? Certainly not today, but perhaps in 50 years?

I mean, a civilization doesn't actually need that much to sustain itself. The basic needs are (a) energy, and (b) materials. Obviously Mars receives Solar power (about 45% as much as Earth per m^2), and it has materials (all basic industrial elements are present in the crust).

The question is, can we start an industry on Mars that is efficient enough today such that the cost of producing and maintain infrastructure (solar panels, mining equipment) is lower than the output from the products? If your solar panel gives 10MJ during it's lifetime, you need to use at most 10MJ (used in mining and manufacturing) to produce it. That's an engineering analysis, and I'm it will be eventually feasible. It also improves with economies of scale.