500.000 $ for a Mars trip ??? This is not serious. Even if you paid 500.000.000 $ per person, it would not be enough money for ticket in the next 15 years. However I think that there would be many people (Chinese, Russian) who would pay 500.000.000 $ (not in cash, but stocks, shares ) or more even for one way flight. But we have to wait until the technology will be better.
Btw. we could have had a human on Mars if we had sent a volunteer instead of the Curiosity rover for a suicide mission. Such a mission is possible to do in the next years.