I think the aim is to leave no possibility that you have missed any market that you can extract a few dollars from
I 'd guess the ultra ultra cheap tickets would appeal to the plane spotting community - a few years back I knew a couple of guys who would turn up at their local airport - fly to Riga or somewhere, spend 1-8 hours clocking local activity and coming back on either the same plane or an evening lo lo lo .
At one point I was doing a pure bum on seat only flight regularly to meetings on a project in the Netherlands - quite strange and occasionally caught the attention of the Organs of the State but worked a treat