Yes, that's usually about right for most exchanges. But if your coin isn't popular enough, they usually will not add it. However, there is a protocol for decen

Yes, that's usually about right for most exchanges. But if your coin isn't popular enough, they usually will not add it. However, there is a protocol for decentralized exchanged called 0x. Any tokens on Ethereum can be traded on this protocol, using websites like Radar Relay.