I've run the math on this a few times ([here](@badrag/the-value-of-renting-to-increase-rank-at-end-of-season-round-2-r2mezf and here). The short version is that the expected value is negative, but only by a few dollars per season. And to me, that is offset by the fun of opening more chests. Yes, it's gambling, but people too often lose sight of the game aspect of all this and think only of ROI.