If median revenue per month is only $133, they suck at gaming it.
I dunno - if you've got things set up so you can run 100 of them simultaneously…
(And I'd guess there's a bit of VC-like speculation going on too - people trying to not lose too much money on the 99 "failures", but making up for it with one single 4 or 5 order of magnitude outlier success.)
Speaking as someone who has purchased multiple sites off of Flippa -- I view any revenue numbers with lots of skepticism. The majority are spammy sites and the remaining sites that are legitimate have often faked/inflated their numbers to entice purchasers.