In fact, many buyers don't even consider the programming language or platform the site is hosted on as being important, so long as they can get it up and running - and it has good PR and traffic analytics.
Hence, why fippa works (at least for selling a site for a few hundred; if you're lucky).
A person is selling a site for $200, and it makes them $50 a month. Many of these sites require little to no maintenance so why are they selling the site in the first place? Surely it's worth keeping the site going until the traffic dies out because you'll make more money that way?
I've been tempted to buy a site on Flippa before, but even though this is an extreme example I've often felt like some of the deals are too good to be true.
Otherwise people (me included) would be snatching them up.
Most of the sites on flippa are newly-created wordpress sites. Often they build a site once, then sell it repeatedly, each time with a new domain name. They can sell them for $60 or something and have a minimal amount of time invested, plus a domain name.
These sites likely will never make their new owner one cent, although perhaps they're not a bad way to get your feet wet.
Anyway, any site selling buy-it-now for 4x MRR is lying about something.