The others are quite clearly marked as estimates, this one not really, and the second estimate from the top in the reddit thread (yielding an estimate of $22,390.37/mo) got the following comment by one jedberg:
> Yes, once again, you are totally accurate. That is almost exactly what it costs to run reddit, as of today. However, with our projected growth, we're looking to be closer to 350K by the end of the year.
note that the comment got that estimate based off 1-year reserved servers, which jedberg's comment suggest is broadly correct rather than 3-year reservations.