Charging for changing economy class seats...***

We just completed 3 month trip in Saudi Arabia and is flying home. We got our flight details and is excited to go home. As per normal, all grab their tickets and try to get a decent seat. Now all.of a sudden you have to pay SAR57 to chamge a seat. No even changing to business or 1st class...just to another economy class seat at the back of the plane. Are these airlines so desperate for money they charging for changing seats? ***???