Mars One is a scam. All they want is money for their crew selection reality TV show. After that has been aired and the money has been collected they will disappear quietly into the night. Mars One can't hope to raise even the smallest amount of the money needed for sending humans to Mars which would be hundreds of billions to a trillion dollars or more.

And that's WITHOUT a plan to return humans from the mars surface back to Earth. If you tried to put a return craft on the surface of Mars the cost would rise even more. But even without a return craft, the costs of sending humans to Mars are insane and they arise when you try to put all the infrastructure on the planet needed to enable human life for months or years (i.e. a safe habitat and energy-creating technology and atmosphere-regenerating technology and water-creating and -regenerating technology and storage space for all that technology). The costs also arise when you try to put the many tons of water, oxygen, food and other supplies on the planet needed for months or years of human life.

And that's not even mentioning any scientific equipment or spacesuits or anything like that. The costs of shipping all that to Mars and landing it in an atmosphere are ASTRONOMICAL (i.e. the cost for building many dozens of rockets, dozens of crafts and many thousands if not tens of thousands items of equipment and fuel of course, so much fuel). A return craft would be a drop in the bucket compared to all that. And all that is not even mentioning the costs for designing the rockets, the crafts, the habitat, the planet-side technologies and testing all of it before sending it into space. A trillion dollars is a very conservative calculation for the costs that would arise even without a return craft.

Look at what the moonwalks did cost per kilogramm landed on the moon. Then consider how many times greater the distance from Earth to Mars is than from Earth to Moon. Then consider what that means for the cost per kilogram shipped to Mars and how much greater they would be compared to the moon shot. Then consider that planetary orbits dictate that humans have to remain on Mars at least a year compared to the three days max Apollo astronauts stayed on the moon. Consider what that means for supplies and equipment which would have to have a mass hundreds of times greater than the mass of equipment and supplies shipped to the Moon (remember all that additional mass is many times more expensive to ship to Mars per kilogramm).

Then consider how much more complex and advanced the equipment would have to be if humans wanted to live on Mars for a year instead of three days. Then consider that all that equipment would have to be developed, built and tested. Now consider what all that taken together would mean for the cost per kilogramm shipped to Mars and the total cost for a manned Mars mission. You arrive at a trillion or two EASILY.