[wotan]

Doesn't antimatter cost about $27B per ounce?

[cabojoe]

"A rough estimate to produce the 10 milligrams of positrons needed for a human Mars mission is about 250 million dollars using technology that is currently under development," said Smith. This cost might seem high, but it has to be considered against the extra cost to launch a heavier chemical rocket (current launch costs are about $10,000 per pound) or the cost to fuel and make safe a nuclear reactor. "Based on the experience with nuclear technology, it seems reasonable to expect positron production cost to go down with more research," added Smith.

[Larry Lucido]

Doesn't antimatter cost about $27B per ounce?

Does it matter?

[orionblamblam]

35 milligrams are all that would be needed to put something the mass of the Space Shuttle into orbit.