JSFiddle - React, Tailwind, and code Playground

HTML

<form name="calculateIt" class="rel-calculator">
		<label>Enter the number of people on your mailing list:</label>
		<input type="text" name="people" id="people">
		<label>Enter the number of irrelevant stories by year:</label>
		<input type="text" name="stories" id="stories">
		<input type="button" name="calculateIt" id="show-result" value="Calculate my cost" onclick="calc()">
</form>        
<p class="calc-result">
	<span id="result"></span> total cost per year
</p>

JavaScript

var formatter = new Intl.NumberFormat('en-US', {
  style: 'currency',
  currency: 'USD',
  minimumFractionDigits: 2,
});

function calc() {
      var people = document.getElementById('people').value;
      var stories = document.getElementById('stories').value;
      //var result = Math.floor(people * 0.2 * stories * 30);
     var result = Math.floor((people * 0.156) * ((stories * 15)*4.2)*12);
	  document.getElementById('result').innerHTML = formatter.format(result);
}