27 years is a life sentence because it takes him to age 81, but I see your point.
Plea deals always involve give and take. For example:
Prosecution:
"You give us something and spare us a trial and we will give you something in return."
Defense:
"Our defendant will change his plea from not guilty to guilty." "Now what is your offer to us?"
Prosecution:
"27 years instead of another life sentence."
Defense:
"Ok, we won't go to trial, please send us the papers for our defendant to sign stating your deal."
You see Alex had no incentive to change his plea to guilty without getting something in return. It always works this way. Another thing, Alex gives up his right to appeal by pleading guilty. That gives finality to the case.
www.law.cornell.edu
Plea bargains are agreements between defendants and prosecutors in which defendants agree to plead guilty to some or all of the charges against them in exchange for concessions from the prosecutors.