Board Thread:ROBLOX help and discussion/@comment-25298348-20150807232052/@comment-33338341-20171012092034

Well, if the month has 30 days, you would get 1800 robux a month. And that's pretty good as it costs about 2 times more than the 800 robux purchase, and it also gives you a lot of other benefits.

P.S. 2x800=1600