There is little hope that chemical propulsion will have alternative orbital launch in near future. Using the same (even optimized) engines and fuel for inter-orbital operations will increase start-to-payload mass ratio exponentially. Roughly, inter-orbital operations and propulsive landing will need the same delta-V as orbital launch one-way only. By hypothetical reduction of launching cost by two orders of magnitude(the maximum whoever could promise), the Mars delivery will cost nearly the same as ISS resupply.
Some projects for permanent human presence in Mars are based on large reusable rockets. May this type of logistic travel support Martian colony for less than $1M per person?
So, sorry, you're asking about, what have we done in respect to thinking about Mars, sort of, colonial systems? The question is, how did I come up with half a million dollar price tag to move to Mars. Well, umm, I sorta started back from the half a million dollar point.