I only recall Lil' Jon & Tha Eastside Boyz and Master P going platinum plus on an indie and that's. Jon did it in '05 w/ Crunk Juice while Master P and No Limit did it in the mid 90's-early 00's. It's not something that's easy to do no matter how huge an artist's buzz is. The artist has to have the capital to fund the distribution of a shipment of 1 million units. On top of that, the promo, marketing, and all of the other business aspects to build awareness and hype of an album are all the artist's responsibility.
Drake did right by signing to a major, because it wasn't guaranteed that all the people who downloaded the mixtape would cop an album especially without the benefits of having a machine behind him.