JSFiddle - React, Tailwind, and code Playground

HTML

<form>
	<input type="checkbox" value="2000">
	<input type="checkbox" value="1000">
	<input type="checkbox" value="200">
	<input type="checkbox" value="600">
</form>

<div>2000</div>

<script>

var form = document.querySelector('form');
div = document.querySelector('div');
price = +div.innerHTML;

form.onclick = (event) => {
	if (event.target.tagName == "INPUT" && event.target.checked) {
		div.innerHTML = Number(div.innerHTML) + Number(event.target.value);	
	} else if (event.target.tagName == "INPUT") {
		div.innerHTML = Number(div.innerHTML) - Number(event.target.value);
	}
}

</script>