You cannot, but occasionally, they make them available on the website and in most of their stores (they did last year for a month, and I bet they'll do it again at some point). Probably since they feel ashamed, they do not post the ludicrous prices on the web.
I smelled them last year, and I must say that I wouldn't have bought even if they costed the regular (ie expensive) Le Labo prices. I think some of their regular offers are better. That said, they have many estimators here on BN, and I think there was a thread on them last year.