https://www.google.com/search?q=Samsung+galaxy+pro+8.4&ie=utf-8&oe=utf-8 finds it here in the USA from 250 to 400 dollars so it can move a lot in price.

Small world that it is I traded a 99 dollar unlocked smart phone for a Samsung Galaxy Tab 3 SM-T3100MKAXAC so that tells you what it may be worth on the street.

I fired it up and don't see anything that would make me pay more than 99 bucks. I'd keep shopping.