[Rasy]

for (var i = 0; i < document.getElementsByClassName('price').length; i++) {
  var a = document.getElementsByClassName('price')[i].innerText.replace(/\D/g, ''),a = +a / 10000;
  document.getElementsByClassName('price')[i].nextElementSibling.innerText = a.toString().replace('.', ',')+'руб.';
}