For a 1/3rd the price you could check in to Soil Master Select, Turface, Turface Pro Leauge as they are all the same and cost about $10 for a 50lb bag.
The AP.com subsrate works fine, I use it and my plants grow beautifully in it.
Yes, it is pretty much just repackaged Turface. If you can get a local store to order it for no extra cost, go for it. Buying a 50# bag online will incur about $30-40 in shipping. AP.com includes the shipping cost in the price, so saying you can get Turface for 1/3 the price is not really accurate, unless again you have access to it locally.
There are many things that are repackaged and relabeled for the aquarium hobby. It is convenience and peace of mind that you are getting something safe for your tank, since many people do not feel like hunting down a particular thing all over their state and still have an unknown.
Caribsea "oolitic" sand is aragonite you could buy as playsand for $3 for 50# of - sold at $30 for 30# at LFS. Most buffers are baking sodas or similar you can buy for pennies a pound, sold at a massive markup. Most any gravel can be purchased by the TON for a few dozen dollars. Filter floss, carbons, foam pads for filters, tubing, etc, etc- all can be had for a fraction of the cost that the aquarium hobby offers them for. You pay for the convenience.