Sure - 20$ to get trolled constantly sounds like a deal.
Here is a idea - everyone pays 300$ a year and that money is divided among the people who actually attempt to make useful suggestions while the trolls get a day deducted from their 'year subscription' for each spammy or troll post.
Or just leave it the way it is and use ad blockers to rid the banners or whatever advertising is bothering you - or just cope with the ads and ignore them.