Update: I can confirm that, with my 30-day e-Tourist Visa, I did not need to show anyone any evidence of having a return flight booked...which is good since I don't have one! I will be leaving India well before the 30 days elapses, and will fly from Mumbai to Singapore, then Singapore to Sydney, before taking Virgin Australia from Sydney back home to Los Angeles.

Getting the e-Tourist Visa was one of the most convenient experiences I have ever had. They say they issue it within 72 hours, but I got mine in less than 24 hours. If you can use it, do it.