In the USA, Aquarium design group sells it:
http://www.adgshop.com/
http://www.adgshop.com/Aqua_Soil_s/21.htm
The amazonia is nice, a 9 liter bag will cover a 20 gal H tank.
So 26$ is pretty good for that.
If you have not tried it, it will surprise you. there is little growth differences between Flourite and EC. Aethetics, weight and rinsing are the main issues there.
But the differences between the ADA As and the others is a lot larger.
Cost is pretty close, some have argued that Flourite or other products are cheaper for them, that's due to local free shipping, sales etc.
ADA stuff does not have that large marketing but over time that will change, the same could be said for Flourite about 10 years or less ago.
ADa As is not to be rinsed prior.
You can also pour it in to an extisting tank without draining the tank etc.
I just add soem okld water/mulm/filter squeezings etc to the bottom of a new tank, a light dusting of ground peat, and add the ADA AS over that 2-6" deep.
It will lower pH, but this is not an issue if you do weekly water changes. It makes using the pH/KH table a little tougher, but there's a simple way around that.
Regards,
Tom Barr