It's currently at 7.7% + $0.25. But it's a bit more complicated than that.

If you want something to sell, you usually have to use their "bump" feature to get it to show up at the beginning of any relevant search results. You give an additional percentage of the sale to get it higher in the listings. If you have a more common item, you usually have to give up a higher percentage to get it noticed.

Once you factor in shipping and everything else, I usually sell most of my items at a loss of 10-25% depending on the item. I've never really made a profit from anything I've sold on Reverb.