Good to see Indo and others spittin game for the up and comers in this thread.
Basically charge what you think you can get and what you deserve. There might be some dudes you dont mind hookin beats to for free or real cheap, while others you charge a little more. I know for me personally years back id charge anywhere from $100-$500 a beat, depending on who the person was. For example my dude Imhotep from Chicago, peplove from Hiero and Bounty Killer, they all dudes i look up to and respect a great deal, so anything i did with them it was for free in the past (It helped us both). While other more underground dudes, i use to charge at least 100$, but if its a super slappin beat ive gotten 500$ before in the past.
My advice is to not over charge though, like the dude Indo he puttin in work like crazy and his beats are very high quality, but he isnt charging 1000$ a beat and what not. His prices are very affordable for the quality you are getting. Dont charge to little, but at the same time make sure not to over charge dudes.
Just my two cents on the topic. For new producers that are up and coming, look at Indo as a good example, he doesnt need to spend a shitload of money or the crazyiest equipment, but the quality in his beats are top notch. He also could charge ALOT more if he wanted to be stingy.