denisgaker,
<!DOCTYPE html>
<html>
<head>
<title>Untitled</title>
<meta charset="utf-8">
<script src="https://ajax.googleapis.com/ajax/libs/jquery/1.12.2/jquery.min.js"></script>
<script>
$(function() {
$(".new-grav").each(function(indx, div) {
$(".btn-grav", div).on("click", function() {
$("input", div).prop("disabled", !$(this).toggleClass("on").is(".on"))
})
})
});
</script>
</head>
<body>
<div class="new-grav">
<button class="btn-grav" id="activevvod-1">
Гравировка на футляре
</button>
<input id="grav1" placeholder="Гравировка на футляре" disabled>
</div>
<div class="new-grav">
<button class="btn-grav" id="activevvod-2">
Гравировка на кошельке*</button>
<input id="grav2" placeholder="Александр" disabled>
</div>
</body>
</html>