are commissions negotiable on cfd's

I have very recently set up a cfd account with my broker with £25000 deposit. He reckons that i should see on average about 15- 20% p.a.return after commission of 0.15% and other expences. Looking at his commission over the last few weeks it seems that on average the broker is earning about £850 a week, about £44000 a year !( nearly 200% on my money withno risk) good luck to him i dont begrudge him earning but considering the risk i am taking i dont think the risk/reward is worth it for me unless he splits his commission or some other basis ie a spread. Has anyone got any suggestions/ideas ? which would be gratefully accepted.

Best wishes