1. An amount between $5 and $10.
2. An amount between \\$5 and \\$10.
3. An amount between \\\\$5 and \\\\$10.
Please include the code chunk abov
A simple trick is to put in a space between the $ and the number.
4. An amount between $ 5 and $ 10.
MathJax should only triggered and activate math mode when it is (first) followed by a non-whitespace character and should end at a $ preceded by something that isn't white space.
It doesn't always work quite right but I tried it on my blogdown setup and that seemed okay.
Also ... (and I have no idea if this could be the reason) ... but which version of MathJax are you loading? I'm including the following code in my pages, and that renders your third example okay too.