A festival in Brisbane, Australia had exactly the same approach.
The festival was Parklife and I think it was back in 2012?
$1 price increase on all cups, bottles and food containers. If you brought the item back (it didn't have to be yours!), you got a $1 back per item. It started off as coupons so you could purchase other goods with the coupon but at the end of the festival you could cash them in.
Never in my life have I gone to a one-dayer EDM festival and went home with significantly more money than I started with.
The economics of the choice being, the festival didn't need to pay for cleaners on significant overtime rates. And we're incentivised because I made a fucking profit from an EDM festival!
For the life of me I can't find an article on the event.
Needless to say after some choice after market vitamins, I was motivated to clean the venue during artists I wasn't too interested in. I was also incentivised since the festival was held in my cities Botanical Gardens which are around the corner from my office.
At the end of the festival, not a scrap of rubbish could be found.
It wasn't an absolute success though. Some people started fishing rubbish out of bins to get their own coin back towards the end...