A Maserati Problem is the kind of problem or issue that your startup company will, presumably, experience some day.
"Some day" being when you're making millions of dollars in revenue, you have 100 employees, and you're driving around in a Maserati.
Calling something a Maserati Problem, then, is akin to saying you probably shouldn't be worrying about it if your closed beta is still 2 months from launching.
Person 1: "What kind of budget do you think we should set for miscellaneous pen and pencil supplies in our supply cabinet, given that a certain number of employees will steal a given amount per month?"
Person 2: "Uh, I think that's a bit of a Maserati Problem."