You have to be an idiot to do this on a week to week basis. Either you are wasting a sick amount of time for only a small, small profit or you are losing.
Well, not really. It's a lot like online poker in the sense that 85-90% dropping money on these sites are out of their depth, so all you have to do is be reasonably solid and you can make some money.
I think a lot of skilled players think that. But the reality based on what i've read, is that 2% of the people win 80% of the money using complicated computer programs.
I think it depends on how you approach it. If you think you are gonna turn $100 into $300k by winning a contest with 100k runners, well you are fooling yourself. That type of thing lends itself well to people who can data mine and spit out hundreds of automated lineups. On the other hand, you can do single entry and small field events that minimize the impact of the "sharks" and that's probably the way to go if you're a casual looking to have fun and make some money.
Again, poker is a fitting analogy. I am not a great card player, but I can walk into a casino and play low stakes hold 'em and always be a favorite to leave the table with a profit. I know just enough about the game that I can consistently beat people who don't know how to play (which is like 90-95% of people really). If I jumped up to high stakes, I'd probably get clowned. Being merely "good" is good enough to beat clueless casuals, but the top level of the game is infested with pros who do nothing else with their time and have dedicated years of intense study to those crafts. You're not likely to beat those guys in any field, whether it's cards, DFS, pool, bowling, or whatever. So while "most of the profits" in poker go to a tiny number of pros, if you have good game selection then you can probably beat micro/small stakes without much trouble.
Problem is that guys see the FanDuel ads on TV and then probably jump into stakes and games that they have no chance of beating.