I might be a little too out of it right now, but what exactly was the reporter trying to say with that? I mean isn't it kind of "No shit! Getting people to Mars will be harder than getting a car battery to cost less than $5K." (Aren't car batteries like insanely cheaper than $5K?)
And somehow this article popped up.. my brain is melting: Tesla's Elon Musk: cheap car battery tougher than Mars. And just in case your question was serious the battery in the original question is presumably the 60 kWh battery that powers Tesla cars. Musk recently mentioned about his goal to reduce the cost to $5000 (at least some time ago they were $10000 apiece).
Yeah I think she was just trying to be kind of cutesy or funny or something and Elon Musk was just like, "Mars?" and he actually said that he does expect to have a mass produced car that will be affordable to the broader consumer market... He also said that his Tesla team and the Panasonic team(their battery maker) have daily meetings pertaining to this issue.