A pretty expensive substitute for compost. It is simply compressed coir, peat moss, and water absorbing polymers and I've found 10 pound bags of potting soil around here for just over $2.00 which means I can buy a lot more of them than this expensive material.

lol, sounds like what i used to use as a substrate to grow portabellas and very much the same as what I currently use for most of my seedlings, although I'm mixing it up myself and probably saving oodles of money comparatively speaking.

60% coco-coir, hydrated from bricks
25% peat moss or finished compost, when available
05% perlite or vermiculite
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Then I mix it all up and add water until it's saturated to field capacity (point at which squeezing it lightly only causes a couple drops of water to escape and squeezing it firmly causes a quick little rivulet of water to run out.

Toss them into 8qt. gusseted bags and steam pasteurize them to kill off any contaminates - all the lovely thermophilic beneficial microbes survive this - for about an hour and after it cools it's ready to be used.

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Might seem a little anal retentive for seedlings but it's a lot better than the fractal sterilization methods of nuking it or dumping boiling water, etc. on it.