Running a blog can be a costly proposition, depending on your needs and the level of engagement you desire. There are many factors to consider, such as domain name registration, hosting fees, and other associated costs. Additionally, there are the costs of content creation (copywriting, editing, etc.), as well as marketing efforts.
Ultimately, the amount of money you spend on running a blog will vary depending on your specific needs and goals. However, it is generally safe to say that it will not be cheap to achieve significant web visibility and traffic.