It's all about the skill distribution - you want to keep them all balanced (like duncan), rather than mono-skilled like Angeloni.
While Angeloni has Colossal JS and 14 DR, he doesn't have a lot else. Duncan has a big spread, highest skill is OD at 13.
You can play with a salary calculator like this one: http://www.buzzer-manager.com/estimation_salaire/
You can read more here: http://buzzerbeater.wgz.cz/rubriky/salary-formula
Ideally, you're looking to build/train a balanced player to maximize efficiency. Right now you should be 'pumping' OD on Angeloni to add value to him.