Here in Albuquerque, we're a lower income sort of state, so the higher end doulas are $600-$750 (JUST sort of bumped up to 750 recently in fact), middle of the road is $400ish, and newer ones like me charge $250-300. I did my first 2 births for free, then offered a sliding scale of $100-300 for the next 3 and got paid the higher end of that.
I would always advise charging at least a little something even though I didn't. Most doulas will tell you that and I ignored that advice to no major detriment...but I do think it makes people take it more seriously and value your services more, as well as making you feel at least a little bit better when you've worked your tail off at a long birth! Your services are worth something always, no matter how inexperienced you may be! Good luck on your doula journey.