I believe it's only available at Best Buy and Amazon right now.
I bought my Samsung Galaxy Tab S 8.4 a few weeks ago. I had originally been planning to buy a Tab Pro 8.4 but when I saw Best Buy's Tab S launch promo, it was a no-brainer. They guaranteed at least $50 trade-in credit for any working tablet (I traded in my 2012 Nexus 7 for $50) plus a coupon for an additional $50 off any Galaxy Tab S model. I ended up paying $299.99 plus tax, which is $30 less than the Tab Pro I was going to buy.