Well, it's not a deposit. It's a tax that manufacturers pay, which finances some make-pretend recycling options. But consumes don't use the recycling options and the electronics still end up on landfills.
I'm afraid this would have the opposite effect though. Instead of donating old phones or CD players, people would have them trashed to get their deposit back.
People are complaining about the current state of recycling, but I save up all my lithium batteries and pay to have them recycled every few years. You can't throw that shit away.
The impact is significant, even if it's such a low amount of money. A €25 deposit would definitely keep people from throwing out these things en masse. There will always be people who will act selfishly and against their self interest, but you've got to be pretty damn rich to throw out €25 like it's nothing.
The result is that homeless people are often going around collecting bottles. On garbage day, I’ll often see at least two or three people walking down the alley collecting bottles out of everyone’s bins before the garbage truck shows up. And in parks you often see homeless people rummaging around the trash cans looking for bottles, or just walking around picking them up off the ground. For the people who are too lazy to handle it themselves, we’ve (unintentionally? Maybe?) incentivized homeless people to be trash collectors and get paid for it. If the deposits were larger, guaranteed this would ramp up.
Plenty of places that take e-waste right now will refurb and resell a subset of the hardware they receive. This would be no different. It's true that this would place a floor of the money required to obtain these devices, but it's not like there would suddenly no longer be used devices for sale.
Only problem I've had sometimes is them calling back claiming that I left them hanging, which actually means a scrappie collected it before they arrived.