Impact of small fields

[Atropos]

Hey folks,
it seems that playing MTT's as ones main game is a bad idea, because the swings in MTTs are so crazy, that you cant guarantee a regular income stream. What I ask myself is, how big is the impact of the field in MTTs? It's quite clear to me, that winning the Sunday Guaranteed tourneys with 3000 players is a longshot, however a highly profitable one. But what's up with the small tourneys with maybe 200-300 players in them?
Lets say I play 200 of these tournies. How high is the chance of a winning player losing money over this stretch, due to variance? How about 500 tournies?
I would appreciate it, if someone could do the math or show me how its done. If no formula or anything exists, maybe empirical data would be valid too [img]/images/graemlins/wink.gif[/img]