I will provide a reproducible example. First, create a new blogdown website with blogdown::new_site(). Then set options(blogdown.ext = ".Rmd", blogdown.methood = "markdown") in .Rprofile. Create a new blog post by running blogdown::new_post("Dollar Signs"). In the index.Rmd file, add this:
Five hundred dollars: \$500
One thousand dollars: \$1000
Two thousand dollars: \$2000
Return to the root directory. Compile the post by running blogdown::build_site(build_rmd = "newfile". Preview the website by running blogdown::serve_site() and type the address it tells you to type in your browser (usually localhost:4321). Click on the new blog post and see if the dollar signs are rendered correctly.