But it’s inaccurate and needlessly provocative to say that the government is killing people through euthanasia. The government made it possible for people to seek medical assistance in ending their own lives.
"Old" people are expensive because as they age, their body degrade and gets harder and harder to "maintain". If you can prevent aging, then you pay a bit upfront for prevention, but then it get cheaper later.
If you want to compare with COVID, it is cheaper to vaccinate everyone than treat the bad cases in a non-vaccinated population
That claim is notably absent from your source.