<input  type="number" class="count-item" min="1" name="comment" max="20" value="1">
    //<input name="order_custom" class="qnt-item" type="hidden"  value="" />
    //<input name="order_custom1" class="price-item" type="hidden" value="2850"/>


     var qntgoods = $(".count-item").attr("value");
    $('.qnt-item').attr('value' , qntgoods);
    var pricegoods = $('.price-item').attr("value");
    var resultsend = pricegoods * qntgoods;
     $('.price-item').attr("value", resultsend);
    console.log(resultsend);