I decided not to go ADA when I caculated that for my 4x2x2 tank, it was going to cost me over $800 for the substrates alone. Amazonia goes for AUD$80 per 9 litres in Australia, and the powder form is even dearer.
I think that I calculated that I would need about 60-70 litres of the stuff when you take account of having a slope from the front to the rear.
I went for fine gravel (black) and Dupla laterite. My plants are going great, although I am not trying to grow particlarly difficult plants, and I already had pressurised CO2.
It is sometimes depressing living in a smaller country with lower economies of scale at work...
I tried shipping it in from the US, but they won't do it so the local distributor has it all stitched up...