How is the zakat calculated for Ta'if rose oil products, knowing that their selling price in the questioner's country is variable and unstable, and there are a few shops that sell them at a price much higher than the purchase price?

Merchandise is subject to zakat al-tijara (business zakat), by appraising its value at the completion of a hawl (lunar year) from the original capital with which it was purchased. If its market value reaches the nisab (minimum threshold) of gold or silver—either by itself or combined with money—then one-quarter of one-tenth (2.5%) of the value is to be given. If it does not reach the nisab, then no zakat is due on it. The appraisal is to be done according to the current market price. If the price of perfume varies, it can be appraised at the wholesale price. Some scholars hold that the appraisal should be at either the wholesale or retail price, depending on the merchant's predominant selling method.