You mean the entire Apollo program cost $145 billion. This is one mission to the moon with much better technology and lower costs. You just can not compare costs like this.
According to the per-year costing in [0], about 80% of the entire Apollo program cost was accrued before the first moon landing. That suggests that even just one mission will come with a substantial price ticket, even if no hardware is built for subsequent missions.
Yes, but analogous 80% of the entire Artemis cost are also already spent and the results are there. Engines, launchers, spacecrafts (Apollo analog maiden LEO flight is expected this spring), electronics, power, communications...
Since the lander and gateway are yet to be built let alone tested (at least Wikipedia still has them as a "concept") it seems too soon to say what the final cost will be. By way of comparison the first full Apollo stack flight was 20 months before Apollo 11, which puts it close to the 60%-spend point, and that was some five years after the LM contract was placed.
[0] https://www.thespacereview.com/article/3737/1