How do you fairly and objectively judge someone's life then?
Last I checked, when people murder multiple people, that means they're a murderer and if they're unable to rehabilitate and continue to hurt people whilst in jail, it's fair to assume they're a danger to society and other innocent people.
Path, just because you believe in "muh morals," that is not an excuse to coddle absolutely horrible individuals. That attitude just enables them to continue to do more crime because hey, they're humans too, that means we aren't allowed to judge them for their actions! That thought process is flawed when it comes to dealing with people like this, whether you like it or not.
It costs $1.26 million to go through the legal trouble of euthanizing someone (http://www.deathpenaltyinfo.org/costs-death-penalty), and between $14,603 and $60,076 to keep individual prisoners per year. (http://thecrimereport.org/2012/02/13/2012-02-the-high-cost-of-prisons-using-scarce-resources-wise/)
Yes but that's in one year. In 20 years or more when you're keeping them for life, it gets up to 1 million, and can cost even more when they're kept in the correct high-security correctional facilities.
Getting rid of an individual who is a massive threat to society and innocent people's lives is a much better option that to actively keep them alive and in good condition, which is a waste of time because it is just allowing the risk to float around wherever they are and rehabilitating these individuals has an EXTREMELY slim chance of even happening at all. It is a waste of time and tax dollars.
Morals don't solve these problems. Taking action to prevent it from happening, will.