It might be a great deal for a qualified lawyer, or a very bad deal for a lawyer who does not know what he/she is doing. There is no way for us to know (and this is not the place to discuss names and details). Meet with other lawyers and choose one you are comfortable with based on their expertise.
The cost will depend on a number of factors including the experience level of the attorney, the area you live in, and the type of petition you are filing for your parents. The amount of money you are describing could very well be fair for the amount of work involved. It makes sense to consult with a couple of different attorneys in your area to see what attorney you are most comfortable with. This will also give you an idea of what others are charging. However, it also isn't wise to go with the cheapest option. You need to evaluate the whole situation.