PERFUME PERCENTAGES
I'm asked almost daily what the difference is between EDP and Extrait, as I offer both options for some of my perfumes.
The image below offers a general outline for your reference. What is good to note is that each perfume house will have their own way of doing things and their own range of concentrations specific to their formulas.
Even more important to know is that
concentration does not always equal longevity or sillage especially in natural perfumery. It CAN .. but it's not a given, because longevity and sillage are primarily dictated by the materials themselves. 
Top notes are the most diffusive and last the least amount of time. Their molecules are the lightest in weight. Base notes are the heaviest and last the longest, and heart notes are everything in-between to varying degrees. For example, one drop of patchouli might last for days, but one drop of bergamot may reach only 20 minutes. This is how we create perfume evolution throughout time on the skin.
Concentrations matter - for cost, for olfactory strength, for the story of the perfume, for specific ingredient safety, and for some, viscosity, stickiness, or color.
Some of my perfumes do not come in EDP dilutions (like Earth Laughs in Flowers) because it is my feeling that they are at the percentage at which they express their best character, and further diluting it would not serve the scent profile or the wear experience.
Difficulty can occur for delicate florals and citruses that live near the top note category like neroli or clementine; to make it last as long as one might conventionally hope would require more base notes than Neroli can handle, and the perfume will become overshadowed or weighed down. Same goes for diluting it too far - the Neroli can become too faint to really get the full feeling, and although it would serve the wallet well to dilute such absurdly expensive materials, it may not serve the perfume or its wearer.
Another more nuanced consideration is how a material behaves at different concentrations. Not only is there alchemy that occurs when materials are blended, but single materials can behave differently at different levels of dilution, sometimes drastically. It's important to have a feel for where a note really sings. Sometimes less is more, and sometimes you need a lot to make an impact. Sometimes the olfactory profile is quite different at different concentrations.
Some of my perfumes are offered in EDP concentration because they are inherently strong, and can beautifully handle further dilution from Extrait to EDP with absolutely no sacrifice of olfactory integrity.
I make my perfumes relatively concentrated. My pure perfume extraits are anywhere around 30% to 50%. This is partially because that's how I like it, and partially because it drives me mad when people wrongly assume that natural perfumes are weak, linear, or don't last. It is also because I am not privy to the good large fancy Italian perfume glass that the big houses are able to source - as the MOQ's usually amount to thousands of pallets of bottles ranging anywhere from $30,000 and up.
Why would it matter beyond aesthetics? Because many botanical aromatics can degrade over time when exposed to air - and with larger quantities that are expected to last longer for the customer, I would need the bottle to be airtight with the crimping method collars of the fancy bottles. Since I am relegated to screw top bottles as a small independent artisan perfumer, I will only offer them in small quantities that you are able to use up in a relatively short amount of time while the perfume is at its best. This will range differently for each fragrance because of the differing evaporation rates as explained above, but could be anywhere from one to ten or more years.
The other reason is that natural materials are exorbitantly expensive - making natural perfumes also expensive, which would make a large bottle unattainable for many folks. Offering them in small but potent bottles is, in my eyes, the best option I am able to provide.
My EDP concentrations vary from around 15 - 30 %, which is often what people consider to be an extrait. In this context it's worth noting that artificial aromachemicals are often times way, way, way more potent, making it necessary to use them at further dilutions, so an EDP of a department store fragrance may be far stronger and far longer lasting than an EDP of exclusively natural materials. Again, this will vary depending on the actual ingredients.
All of my samples are in extrait concentration unless otherwise noted for a particular perfume, i.e. an eau fraiche or EDC which I make once in a blue moon.
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