It depends on the point of Acer, which also the price of this "metal part" appears. Since most customers are upgrading their laptops, it is also determined not an absolute mass product. It would be better still if the hard disk frame would have been built the same as delivered.
This price and "screws" policy enhances not just the reputation of the brand Acer in my eyes. Such is life but you have not so welcome. One can apparently be happy that this part does not cost 50.
