The first collected edition of Shakespeare's plays was printed in 1623, several years after the author's death, and is known is the First Folio. (Later editions are known as the Second Folio, etc., and have less authority than the First Folio.)
According to the Wikipedia article about the First Folio (emphasis added),
It is believed that around 750 copies of the First Folio were printed, of which there are 235 known surviving copies.
One of the sources for this statement is the article First Folios at the Folger (emphasis added):
Researchers believe that about 750 copies were originally printed.
(The two other sources are newspaper articles.)
However, according to the article First Folio in the online Encyclopaedia Britannica (emphasis added),
The actors John Heminge and Henry Condell undertook the collection of 36 of Shakespeare’s plays, and about 1,000 copies of the First Folio were printed, none too well, by Jaggard’s son, Isaac.
I believe I have read elsewhere (in books) that (around?) 1,000 copies were printed, but I can't exactly remember where. What are such estimations based on?