Why would they end up in a landfill? You can also set them up inside your garden if you end up in a regular house, or mount them to the outside wall, or sell them to the next renter of your old apartment, or sell them on eBay, or...

The panel is just a regular rooftop solar panel in a slightly different form factor. The RoI is so low because you are skipping the expensive installation phase. That's literally all there is to it. They'll last a year or 20, and you can install them anywhere there is some form of sunlight.

Energy-wise you're recouped the production cost after as little as 1 to 3 years. You have to try really hard to have a solar panel be a net negative. Just don't place it indoors or in your basement or something and it'll work out just fine.