If every player is of the same skill level you are on average getting over 100% rakeback if you stop after your 13th sng win at each level. Obviously variance/not every player of the same skill changes that.
That's even all the way down to the $1.50s where rake is higher
edit: I'm an idiot. I thought the prizes kept jumping at the same rate. At the $200 level you're only getting a 5 buyin bonus. Where as for the lower ones you're getting a higher percentage.