I should have caveated my article that I think, as a result of the reward rework which moved a lot of rewards to Diamond/Champ, the ROI is going to be worse in lower leagues. So it might lean towards renting in lower leagues, but I don't have any numbers one way or another to check.

Although you could do a similar exercise to what I did here to check for yourself: do the season reward lookup tool on splex and see what you've earned on average the last few seasons, and then compare to how much splex says you could earn by renting your collection out.