Somebodies livelyhood is always going to be an emotive subject. The hard reality of course is that an employee is simply another commodity. If you cannot utilize that commodity profitably and effectively, then there is no point in hiring it. The author of this thread was questioning the viability of one person faced with redundancy sharing the "job" of another person who was willing to do so, from an employers point of view.
A business is an entity faced with ensuring its survival by making a profit. It is not a charity or a social service. If 10 people are made redundant, it saves the business nothing at all by having them share their jobs into half as many units. Only if 10 people not faced with redundancy were willing to share their roles at a salary less than 50% of that they were previously on would there be any argument for neutrality of cost.
What you spent on your training, medicals or currency is of no meaningful concern to the business, that is your concern. Your commitment to the business is what they paid you for. If they are no longer paying you, they will not expect any further commitment.
I am very sympathetic to your viewpoint, and completely understand where you are coming from. However putting the emotion to one side (as a business normally will,) the mathematics of the equation are much more simple and clear cut.