The auto bid has really made harder to find good deals. Before I could easily trade my time for a better deal since I could be digging peakmonsters constantly.
But I think you can find rentals for a little less than what you said, maybe the difference between the amount I used in the post and the one you put here is that you're probably renting cards that you use and that are good for the League gameplay, and I was just looking for the cheapest power available.
Still thanks for the comment and always appreacite the feedback!