I have been hanging wallcoverings professionally for over 20 years. So take this to the bank.
To find a good contractor, ask your friends. All of them. Check references and ask for professional references as well (Other contractors in the same field)
A good paper hanger is worth the money when you figure that you don't want to pay for the paper twice.
When I measure for paper, I figure on 25 Sq Ft per roll and usually charge between $30 and $40 per roll with all prep and hanging materials included (adhesive, razorblades, sizing, etc.). Removal of existing paper is "Estimated" at $.90 per SqFt, but is belled at $30 per hour. Kitchens are NEVER hung by the roll because if I hang 8 rolls in a Bedroom and it takes me 6 hours, I do well enough to pay the bills, in a Kitchen 8 rolls could take a couple of days because of all the corners that have to be cut around.
Looking at the price quoted, I don't think anyone is out of line, as long as they do quality work. That is the most important question.