Same thing was happening at the cricket world cup, £1 for a commemorative plastic pint pot and there were loads left in the stands at the end of games, kids were going mad collecting them!!!!
They do it all over in Germany. Even with normal bottles from the shops. You can take them back and get money for them. Homeless people usually collect them all and get some money and the streets aren't littered with bottles. Win win.
Reminds me of a night in Newcastle when I was a student (1975 ish). It was back in the days when you got 5p back for your empty bottles. Anyway to cut a long story short, a mate had an old Mini traveller (estate) and we toured round several parties and a queue of people outside Virgin records (for Led Zep tickets) and filled the back of the car with Brown Ale bottles. I think the 3 of us got about £5 each. The landlord at the pub we took them to wasn't too happy.....
They do that at Toulouse in France for Rugby league. A few kids were collecting the cups at end of game. Gotta admit I left mine and didn’t get my euro back