Locks will only ever be a minor deterrent imo. The problem is that police in most places don't even try to go after bicycle thefts and the would be criminals know that.
If governments took bicycle theft as seriously as they did horse theft in the 19th century, then few criminals would even attempt to steal a bicycle if it had some basic protection like a cheap lock + a camera pointed at the bicycle rack.
In my region, it seems that expensive stolen bikes mostly go to eastern Europe, Ukraine and Romania in particular.