You can only charge what the market is prepared to pay.
If you're the only person in the world who can do what you do then you can charge lots, if every man and his dog could do it then lots less.
If you're not making widgets then the cost of inputs is less of a factor, but you do have to pay your bills so if the market isn't willing to pay what it takes to keep your head above water then find something else to do.
As I keep saying to self employed people, being a great electrician/plumber/consultant/dog trainer/bog cleaner, etc isn't all that important, you've got to be good at the rest of it. If you don't know what the going rate is for what you're doing then you're in the wrong job.