Often they are cheap because airlines open their bases in exotic places and the regional local govs, who invested heavily in an airport as part of muscle flexin

Often they are cheap because airlines open their bases in exotic places and the regional local govs, who invested heavily in an airport as part of muscle flexing, subsidize the carriers to avoid having a ghost airport. Modus operandi or Ryanair for a while. (But also connections between major airports in EU can be cheap if booked in advance).