There are different outlets that you can take when making a website. The cost of a website is also a ratio of your time, knowledge and budget. The greater your time and skills - the cheaper you can build your website. On the other hand, you may need to spend more money for a professional website if you do not know what you are doing.
The cheapest route to do is go to a hosting company such as Godaddy and use their basic hosting package plus domain to create a simple brochure website. This package can be had for roughly a $100/yr. They offer a basic site builder and domain.
The problem is that its not very intuitive at that rate and the results aren't necessarily professional if you do not know what you are doing.
On the other hand, a good professional freelance designer should charge roughly $1400 for an effective website. Then, you will have varying hosting fees for additional years.
You can get lower quality designers, part-timers and students for cheaper rates but again you are trading affordability for time-involved, less security and quality.
There is a third alternative with sites such Intuit Websites, Wix and MiracleSites that provide a more user-friendly approach. You get a fully ready to use website that is easy to manage right out of the gate. These systems are roughly 10-30/a month to use and vary in their features and customization. The cheaper ones are generally limited in their available features and number of pages whereas the higher end ones give you full customization and pretty much any feature you'd need.
Some of the third alternative provides custom website design but they generally all provide cheaper theme based websites that vary in their quality.
I hope this reply helps. It all comes back to the tradeoff of time and skills versus to price. If you don't have time because you need to focus on your work and personal obligations, you will need to spend more. On the other hand, you may get away with a cheaper website if you can devote a large amount of time to building it.
Generally, a web designer will take a full month to build you a professional website and they have the necessary skills. This is to give you an overview of how much dedication that would need to be involved to DIY it.