To understand this, you have to realize how it is packaged. The aragalive isn't just scooped out of an established tank or anything. They take their normal bahamas oolitic sand and rinse it in SW, then add some aerobic bacteria to it before packaging, something like you would find in a bottle on the store shelf. BioSpira and such. This bacteria is inactive, and there is nothing in the sand to activate it. It doesn't die off, and lasts just as long as it would in the bottle on the shelf. That's why you find a best before date on aragalive. It sounds to me like the ammonia spike 4 days after the LR was added is directly related to the LR, not the aragalive. Ammonia spikes don't happen in one or two days; they naturally occur as a result of ammonia being released over a period of time and exceeding the capability of the aerobic bacteria in the tank or LR.
I agree it's not really worth what some places charge for it, but the convenience of not having to rinse it coupled with the instant addition of beneficial bacteria makes it worth it if I can find it for a reasonable price. I will pay double for this as compared to bulk dry sand just for this reason. I happen to like the palms of my hands, and couple that with the cost of that much BioSpira or whatever and it's a decent deal IMO.
If you're adding it to an established tank, it's also great because there is minimal clouding if it's added properly, they do a great job of rinsing it
