But falcon 9 is using a time tested approach and has safety systems. The starship has no backup if for some reason the engines fail to start…?

(For the passenger angle)

I don’t think the limiter to mars is cost to orbit: - Having a vessel where people can live for a couple of years - finding someone willing to take the (most likely) one-way ticket to mars - all the challenges of having a mars habitat. Radiation, dust, etc

Reducing the cost: sure, starship has only been launched with no payload so far so the numbers are yet to be determined… and it’s only impressive (theoretical) numbers are to LEO.