I believe they were randomly selected and it had nothing to do with how much you buy. As to how they got into that pool to be selected, I don't know.
Just did that and nothing has changed.
The only thing I've been able to get was the Northern Lights foamposites, but I still think I have a better chance copping when they don't do a raffle. I've never won a Nike raffle online for a store location or on SNKRS.