Well a new
4TB WD Black is about $215 dollars, BUT that also comes with a full 5 year warranty from the date of purchase and you know for certain that it will be in good shape.
If you need an extra drive that WONT have critical data on it then the Ebay drive might work out OK, but you'll never know for certain until you receive the drive. It might have bad sectors. The warranty might already be void.
Personally if I were going to spend $135 on a 4TB hard drive I'd get the
WD Blue. It only has a 2 year warranty, but I'd know for sure that for 2 years any defects would be covered and I wouldn't have to worry about a drive that has already been mistreated.