How much would a round trip to Mars cost for three astronauts in American dollars ?

If they go via Greyhound the trip will take at least four and a half years and cost $6,000,000,000.

Honestly dude, I don’t think that’s a question any of us here could answer, as the cost would depend on a huge number of factors both within NASA and external to NASA.

It’s longer than a year to go round trip. If you go the quickest way, playing off when earth and Mars are approaching each other, you can get there in five months. But then the return will begin when conditions are not favorable for a short flight.

Plan on about 5 months to get there, ten months to get back, if you can get back.

Most calculations for a (wo)manned Mars trip are for one-way trips. The expense of trying to carry enough fuel to return is enormous.

@Quakwatch is correct. Any dreams and models being created for a manned visit to Mars is based on one-way trips. Then again, if you don’t want to land on Mars and just do a bit of an orbit, if you get the Indian’s to do it, it will be a fraction of what it would cost the Americans to do. Here is an article about how much their space probe cost. http://www.newsweek.com/how-india-achieved-cheapest-ever-interplanetary-mission-mars-273588

Some private company is (or was) tossing about the idea of a one-way trip to Mars. NASA, on the other hand, is not, and would not, even consider such.

Here is the idea and plans from the One Way Trip. http://www.space.com/27517-buzz-aldrin-one-way-mars-trips.html