The following organizations offer reasonably priced euthanasia and cremation services.
The Anti-Cruelty Society, firstname.lastname@example.org, (312) 644-8338 is a free (suggested donation) option for pet owners who would like to be with their pet for the euthanasia, and offers options to receive the ashes. You may also bring a deceased animal for cremation.
Chicago Animal Care & Control, email@example.com (312) 747-1406 Euthanasia is $10 and does not require an appointment, but you will not be allowed to be present for the euthanasia or receive ashes back. Cremation for an already deceased animal is free. Hours are are 12pm-7pm, 7 days a week.
Oak Elm Animal Hospital, 1445 E Oakton St, Des Plaines, IL 60018, 847-759-1440