My cost in materials to grow a tree aloe to 3 gallon size (approximately when they flower) is about $5, without the benefit of scale. The sale price for that size would be about $20 if you were to seek one out in say a nursery in San Diego, where they are relatively available. But as I like to think, the one-of-a-kind hybrid tree aloe is priceless.
The leaf wouldn't do you much good (most of these are not medicinal aloes) and it does not help with propagation. The only medicinal aloe pictured above is the Cape aloe with the red flowers in the first picture of six. That is one case where the leaves are harvested and the juice collected for herbal medicine. I have not tried this but it's the right plant.
The plant in your picture looks like Aloe vera, another medicinal aloe, whose main use is topical, for skin problems.
