deviantART premium membership is $5/month.

Members can get a discount: $8 for 3 months (save 46%) or $30 for a year (save 50%).

Premium Member community benefits:

1. Instant community privileges incuding multiple commenting.
2. Access to exclusive archived content.
3. Can admin more than 3 groups
4. Change your username

Other Premium Member benefits:

1. 10GB storage in your Sta.sh instead of the default 2.
2. Stats about visitors to your pages.
3. Buy your own work at a 50% discount.
4. Set your own Print prices.
5. 10% off Prints and deviantART Gear purchases.
6. Portfolio for self-promotion.
7. Custom skins for your journal pages.
8. No ads.

deviantART user stats:

"As of August 2010, the site consists of over 14.5 million members, and over 100 million submissions, and receives around 140,000 new pieces of art uploaded daily. In addition, deviantArt users submit over 1.4 million "favorites" and 1.5 million comments daily. The domain deviantart.com attracts 36 million visitors annually according to Compete. As of July 2011, it is the 13th largest social network with 3.8 million weekly visits."

2010 Revenue: $10 million, from premium membership, prints, and gear.

This is potentially brilliant. 

Let people comment and when trolls come to argue with them, they must pay to have the final say.

Zach, I agree.

There are plenty of other reasons why someone would want to upgrade to premium membership, so I wonder if this is mainly a way to protect premium members from casual trolls.

Btw, the image above comes from deviantART artist Slawa: http://slawa.deviantart.com/gallery/

More of her work:

I see a theme here...

you no like kitteh?

I love kitteh!

Thank you for sharing this deviantARTist:

http://hoschie.deviantart.com/art/Thinking-cat-346209983