Look at LustICO for example, they have already raised more than 1 BTC and have also been labelled as scammers. Even if they had paid a fee, they would still have surely gone a head with their operation.
The idea would be that 95% of the ICO scams currently being started would be blocked as many of them are literally thrown together for a couple of hundred bucks of expenses at most and wouldn't have the means to raise several thousand to pay a posting fee for an announcement thread. Stopping the plethora of cheap-ass scammers would at least lessen the number to a more manageable degree and allow time to investigate the more devious and determined fraudulent ICOs.
It isn't to say that anybody who paid the fee would be considered legit, no, it is simply to throttle the flood of ICO threads sufficiently that we can at least have a fighting chance of exposing the criminals and the con-artists.
Now that you put it that way- true, it would greatly help the reduction of cheap ICO scams. Still, maybe not 95%, but it would certainly help clear out more time to focus on harder, more dedicated scammers. In terms of value and funds saved through this introduction, I can see the 95 come to play.
Also, if an ICO is clear scam and they have run off with a large sum of money, how often is legal action taken? As the scammer/ scammers may be overseas and that can complicate the problem even more.