BlackJack,

I formed my opinion based on interviews and docs. where the key players spoke for themselves...Azie,Alpo and one of Rich Porter's sisters.

I tend to think that Po told the truth about the Rich situation. Alpo had been targeted in an attempted kidnapping in DC years before. He was shot and hospitalized for a while. So this ruthless cunning street dude became even more ruthless and cunning (and paranoid). Killing Rich for lying to him and ripping him off seems like what Po would do. If he was doing that to somebody, he'd fear being discovered and being killed also.
In the interviews, you see that he fully understands that in the streets, once person has no use for you, you get killed. He mentioned repeatedly that how he was able to handle/control a DEMON like Wayne Perry. He said that he kept WP away from the details about stashes/money because he was worth more to him alive than dead.
Po's main value to any DC guy is that he was plugged into to NY area connects directly. He could match or beat the prices that DC drug dealers were paying to their other suppliers.
Rich was valuable to Po in that he was able to maintain relationship to their NY connect....and help provide Po with steady supply of coke.

The story of killing Rich and the reasons makes logical sense. In fact, that's the only way it makes sense. Why else would Po kill Rich if he was helping him make money?