JSFiddle - React, Tailwind, and code Playground

HTML

<div class='form-group'>
  <label class='control-label' for='custo'>CUSTO 1</label>
  <input type='text' class='form_campos calc' id='custo' name='custo'>
</div>


<div class='form-group'>
  <label class='control-label' for='valor_pallet'>VALOR 2</label>
  <input type='text' class='form_campos calc2' id='valor_pallet' name='valor_pallet'>
</div>

CSS

body {
      font-family: Verdana;
      font-size: 12px;
    }
    
    .form-group {
      position: relative;
      display: flex;
      height: 45px;
      float: left;
      margin-right: 2px;
    }
    
    .control-label {
      opacity: 0.4;
      pointer-events: none;
      position: absolute;
      transform: translate3d(5px, 22px, 0) scale(1);
      transform-origin: left top;
      transition: 240ms;
      z-index: 2;
    }
    
    .form-group.focused .control-label {
      opacity: 1;
      transform: scale(0.75);
    }
    
    .form_campos {
      height: 20px;
      color: #484848;
      z-index: 1;
      align-self: flex-end;
      font-size: 15px;
      padding: 5px;
      outline: none;
      border-color: #484848;
      border-style: solid;
      border-bottom-width: 1px;
      border-top-width: 0;
      border-right-width: 0;
      border-left-width: 0;
      background: transparent;
    }
    
    .form_campos:hover,
    .form_campos:focus {
      border-color: #1E90FF;
    }
    
    .calc, calc2 {
      width: 123px;
    }

JavaScript

$('.form_campos').on('focus blur', function(e) {
  $(this).parents('.form-group').toggleClass('focused', (e.type === 'focus' || this.value.length > 0));
}).trigger('blur');


$(document).ready(function() {
      // Qando o valor do campo mudar...	
      $('.calc').blur(function() {
        var custo = parseFloat($('#custo').val().replace(",", ".")) || 0.0;

        $('#valor_pallet').val(custo).trigger('blur');

      });
      
      });