I've used the Spigen and many other expensive screen protectors over the years. Also tried the iSmooth for my Note 2. You get 3 protectors for $9.99. No difference from the more expensive ones. The exact name was Ultra Clear Screen Protector.
That SP doesn't have 10H hardness. It's comparing it's hardness which it rates as 9H as being almost as hard as a diamond, which tops the scale at 10H. In fact, it doesn't have 9H hardness either... None of these SP's are actually 9H, given that any of them can be scratched by common sand, which is typically about 7H (a lower rating cannot scratch a higher rating).
9H and above will do just fine, I have also used 8H flexible ones and they worked just as well. Its all about not buying the sketchy off-brand ones you never heard of or no one on the forums has used before. Spigen clearly dropped their prices because the competition is there and their products are just as good.
I have a $7.50 temp glass on my note 3, even got a spare. I had the $35 Spigen but something was wrong with it, got a refund and got the cheap clone, it has been perfect. Will get one for the note 4 when I get one.