JSFiddle - React, Tailwind, and code Playground

HTML

<form id="box">
	<input type="checkbox" value="2000" name="guide" onclick="pricer('guide')">
	<input type="checkbox" value="1000" name="lunch" onclick="pricer('lunch')">
	<input type="checkbox" value="200" name="hotel" onclick="pricer('hotel')">
	<input type="checkbox" value="600" name="scooter" onclick="pricer('scooter')">
</form>

<div id="full-price">2000</div>

<script>
var elem = document.getElementsByTagName('input');
var div = document.getElementById('full-price');
var price = +div.innerHTML;
var box = document.getElementById('box');

function pricer(name) {
	var element = document.getElementsByName(name);
		if (element[0].checked) {
			price += +element[0].value;
			div.innerHTML = price;
		} else {
			price -= +element[0].value;
			div.innerHTML = price;			
		}			
}
</script>