JSFiddle - React, Tailwind, and code Playground

HTML

<body onload="buybalance();">
		
		<center>
			<button id="bttn">Купить статью</button>
			<br>
			<b>Баланс: </b>
				<div class="result">
					
				</div>

JavaScript

function buybalance(){
  var result = document.querySelector('.result');
  result.innerHTML = '5000';
  document.querySelector('#bttn').addEventListener('click', buy);
}

function buy(){
  document.querySelector('.result').innerHTML -= 250;
}

buybalance();