Well I don't know about most people, but I usually wait for fighting games to go on sale before I will buy them. Mortal Kombat especially. Not because I don't want to support it, but because MK usually will drop an expansion and you're looking at over a hundred bucks plus just for one game. I love MK, but I just don't think any game warrants over a hundred bucks.
MK1 is a solid game all around. I do think that any fighter isn't worth 70.00 bucks though. The expansion is nice, but shouldn't be more than 40 bucks... I mean come on