COSS is not big exchange. It in TOP 100 in trading volumes. But EDC has listings in many others exchanges, so traders will have more choice of exchanges. It will be promotion of EDC token on COSS exchange.
Listing on exchanges costs a lot of money. It is very good that the project is developing and adds new listing. It will help to the worldwide development of the project.
It is not always necessary to pay for listing on exchanges, even on top-end ones. Look at the model of the Binance exchange, they are now actively adding new projects.