According to the M&A investment agencies, the value of Kamagames is at around $500 million.
So the answer to the question "why are they making a token sale?" is just a one (I found it in WP):
"The company will use the Token Sale model to further expand its network of clients and to continue to deliver first-class gaming experiences and services worldwide"
By the way, has anyone found on the wp how the funds raised during the token sale will be used? How exactly the company is planning to expand its network of clients. Maybe they are going to buy some messenger or smth to get synergy effect?