For most web designers, pricing a project is definitely not the highlight of the job. Nevertheless it is something that they’ll have to deal with if they’re freelancing or working for a small web design agency.
Determining how to charge for web design and development is never easy because of one particular reason: there’s no exact formula.
Both pricing methods have pros and cons, and deciding how to price your project is going to be largely dependent on how you work. If you already have a good idea regarding what kind of time your projects require and how much value your clients place on different kinds of work, then charging per project can work really well. But if your clients have a tendency to make changes to scope midway through a project, charging per hour is a better option because then there’s no need to re-quote, and you’re only obliged to remind them that changes mean extra time.
In conclusion, billing process you choose should be determined per project, per client. You will find your ideal pricing method for each project type and each client. Just be prepared to make mistakes along the way.