This is dependent on a lot of things.
First, some people charge per project. Other charge customers an hourly rate.
Even if you decide to charge customers per project like we do at work, behind the scenes you're still calculating that partly based on your hourly rate and project costs.
So how do you determine hourly rate and project costs?
Project costs are pretty easy... How many stock photos might you need? Roughly how much do they cost? Does your client require a domain? Web hosting? How much will that costs? Are there any other costs associated with this project?
Hourly rate is tricky... what is your time worth? That depends on a few things. Your skill level, your demand, and what the market will bear. I can't tell you what that is.
Many times people who are just starting out learn what their rate is through trial an error. Some will price too high and lose a few jobs to competitors because they can't justify the costs based on their skill level, or any additional value adds. Some will price too low, and get in over their heads on projects.
It's a learning experience and we've all been there. And hourly rates do adjust as market conditions change, or skilled people enter or leave the workforce.
I hope this helps somewhat.