The slide deck at
https://www.obrc.com/Content/Reports/OBRC%20Quarterly%20Repo... says $34M/year, so agrees with you.
As a theoretical point, even with a 100% return rate, it's still possible to make money on the float. Buy a 12-pack, deposit $1.20, return 1 week later, get $1.20 back, but in the meanwhile that buck-and-change could make ~1/50¢ in interest.
The same report says they do about 2 billion containers / year, which at 10¢/container is $200M. In the optimistic case of 1 year between purchase and return, assuming 2% interest, that's $4M. Assuming 1 week, I think it's $100K, so not much.
A more likely income source is the profit from selling relatively clean metal, glass, and PET. That report says 151.0 M Aluminum Cans per quarter. I see numbers around 2¢/can for the metal value, so that's $3M/quarter or call it $10M/year.
So even with 100% return rate, there is still money coming in. Just (as you say) not enough to pay for the program.
FWIW, https://www.obrc.com/Content/Reports/OBRC%20Annual%20Report%... says that there was "$25 million" in "Estimated value of 2017 unredeemed deposits". That plus the Al can value is easily enough to pay for the program.