Bulldog did provide some numbers and it was confirmed by others. Essentially they rent cards and are able to easily get 2x the value of the rentals using this "exploit" and one can then deduce that this is likely why we see so many rental swarms in Modern these days.
As far as affordability, one thing I've been thinking with season rentals is that we should have a 1 DEC floor on season rentals. Meaning if you want to rent a card below 1 DEC per day, you can but you have to commit to spending at least 1 DEC to rent that card. I'd sincerely hope that's how the team looks at it. After reading the proposal to go to a 1 DEC floor, that seems in line with the wording of that proposal.
On a side note, I know this may not impact you if you're only renting for brawls/tournaments, but as a user I absolutely hated the daily rental system. I'd try to rent for like 5-10 days so I don't have to check every day and then they're constantly getting cancelled and repriced and then I have to deal with it all over again. I do genuinely agree that moving to "season only" would be aa better end user experience in that regard.
RE: SPS Governance Proposal - Make Rentals Seasonal Only