When I was at Conneaut Lake Park last fall I payed $0.75 for a game of Mortal Kombat 2, and oddly enough Primal Rage was set to $0.50, so I played a game on there as well.
I guess that's why shelling out ~ $8.50 for the Mortal Kombat trilogy (my 3 favorites in 2D) on Steam didn't phase me. Granted getting it on MAME is "free", but I liked supporting the company that owns the IP and maybe the latest MK will come to the PC?