I’m sorry but they just aren’t in my opinion, definitely not at the 15% commission level.
Now don’t get me wrong, I don’t mind paying 15% if the service is worth it. If I can only sell a domain for $1,000 and you can obtain $2,000 for it, I’d gladly pay you 15% because even after subtracting your commission, I’m still left with $1,700. Way better than the $1,000 I can obtain. I’d even be willing to pay 30% because hey, subtract your $600 commission and I’d be left with $1,400 which is still considerably better than $1k. Even a 40% commission leaves me $200 ahead… you get the point.