I'm all for that, after all one can decide what to do with his/her life and how to end it. But I think it would be much more fair to give people another choice: being cryopreserved. Sounds futuristic, but I don't see anything futuristic in storing humans in a tank of liquid N2. The technology to do this on scale is half a century old.
Of course euthanasia is cheaper than cryo, and that makes us ask ourselves another unpleasant question: What is the real market value of human life? Is it really lower than the price of infrastructure for preserving humans in liquid nitrogen?