Start from the same bottle
Look the fragrance up on the price check and read the personal sales column for the same size. The range runs from the lowest asking price to the typical one. Typical is where most bottles change hands; the low end is a seller who wants it gone this week.
Match the concentration as well as the name. An Eau de Toilette, an Eau de Parfum and an Extrait of the same fragrance are different bottles with different prices, and so is a flanker with one extra word on the label.
Price the perfume, not the glass
A bottle is worth the perfume left in it. Say a 100 ml bottle typically sells for $200 full: that is $2.00 per ml. At 80% full it holds about 80 ml, so the same rate puts it near $160. The price per ml calculator does the sum for any asking price.
Partly used bottles usually sell a little under that straight figure, because the buyer cannot know how the bottle was kept. Sizes matter too: a larger bottle nearly always costs less per ml than a smaller one of the same fragrance, so compare per ml across sizes, not bottle to bottle.
Adjust for what comes with it
The same fill can sell for quite different prices. What usually moves it:
- Up: the original box and cap, a sealed bottle, a batch from before a known reformulation, a limited bottle, or a fragrance the house no longer makes.
- Down: no box, a missing or cracked cap, a sprayer that sticks, a faded label, or a bottle kept in heat or sunlight. Testers sell under boxed retail bottles for the same reason.
Check it against new
Before you settle, look at what a new bottle costs at retail and on the gray market for the same size. A used bottle rarely sells above a new one on the gray market, unless the fragrance is discontinued or the batch is one collectors look for. Agree on shipping too: it is often added on top of the asking price.