Screen protectors are the biggest scam in the touchscreen market. Most modern phones/tablets use Gorilla Glass and are nearly impossible to scratch under ordinary use, unless you are a diamond miner I guess.
Plus screen protectors make the touch screens far less sensitive and add unneeded blemishes.
Here's a scratch test video for you.
Don't get scammed.
At nearly $20 a pop... nah. I'd probably go through $100 of them, trying to get it just right.
At my Best Buy they will install a protector when you buy it and a device at the same time and they seem to have a lot of practice putting them on because they come out great