Scarcity can apply to time (limited-time offers) and also to quantity. In the case of The 5th, it's both: 250 new pieces available on the 5th of each month. But there are other notable examples.
Tell me, do you think a book can be worth $400? The expert marketer Seth Godin certainly believes it can. 6 years ago he released a book and charged exactly $400. He also wrote a blog post
to convince the fence-sitters of the book's worth.
The devil is in the details here: 1) Seth Godin is a renowned expert, 2) he wrote a massive book (800 pages long) and 3) only 2,400 copies were released.
In the end, he sold all of them.