Why can a ten-millilitre bottle cost anything from a few tens of thousands to several million dong?
The answer lies almost entirely in one number: extraction yield.
A gap of tens of times
Lemongrass gives about half to one per cent of the mass of fresh leaves. One to two hundred kilos of leaves give a kilo of oil.
Lavender needs about a hundred and thirty kilos of flowers for a kilo of oil.
Rose needs several tonnes of petals for a kilo, depending on the variety and the method. That is why real rose oil is among the most expensive in the world.
The same process, the same level of labour, and the difference in raw material going in is tens of times.
Three factors on top
Harvesting labour. Jasmine must be picked by hand, and in step with its species’ rhythm of scent — Arabian jasmine at night, the Grasse species at dawn. No machine can do it, and the picking window is very narrow.
Growing time. Sandalwood needs decades to accumulate enough fragrant heartwood. The capital lies idle in the ground all that time.
Biological scarcity. Agarwood forms only when the tree is wounded and infected by fungus. You do not harvest a product but a scar, and not every scar yields good agarwood.
Why this matters when buying
Price is not a reliable indicator of quality, but a price too low for the extraction yield is a reliable indicator of a problem.
If you see rose, jasmine or sandalwood oil at the price of lemongrass oil, there is one of three possibilities: it is a synthetic fragrance, it is another essential oil with fragrance added, or it is carrier oil with a little real essential oil in it.
None of the three is what you think you are buying.
The number to know before buying
Before asking the price, look up the extraction yield of the oil you are interested in. It gives you a reasonable floor, and any price below that floor deserves questions.
It is also the easiest check in the whole of Part Four: it needs no equipment and no analysis, only a division.