Pricing
Free.
That is the whole page. No trial to run out, no paywall in front of your own shelf.
Why it costs nothing
Olfa is small and new. Charging for a collection you have to build yourself, before it has earned the trust, would be the wrong way round. So it is free while it finds its feet.
If that ever changes
A paid tier, if one ever arrives, would be for something new rather than for something you already have. Your bottles, your wearings and your notes stay yours either way, and you can delete the lot from inside the app whenever you like.
Free while Olfa is finding its feet. Nothing here is a promise about every version of the app forever, and it would be dishonest to pretend otherwise, but the shelf you build is yours to keep and to take with you.