I highly doubt SnapChat's audience of majority less than 18-year-old population (with most in their early teens) are going to pay $30 a year for a way to send auto-deleting pictures to each other. Especially when there are numerous other free multimedia messaging apps. Getting even 1% of that audience to pay would be impressive.

An RPM of $2.50 is also equally unrealistic for an audience of the mostly non-credit-card holding teen demographic, even more so when they're looking at the autoexpiring content for mere seconds before moving onto reply. Not only that but I'd bet a lot of those snaps per day come from a small subset of the 10M users.