^\d+(?:,\d{3})*\.\d{2}$

<input

    type="text"

    min="0"

    maxlength="20"

    pattern="^\d+(?:,\d{3})*\.\d{2}$"

    pattern-invalid-message="Apenas valores monetários. Ex: 1000.50 | 1000 | 15 | 0.00"

    required>

​

<script>

    document.querySelectorAll('[pattern-invalid-message]')

    .forEach(input => {

        input.oninvalid = function(event) {

            let invalidMessage = event.target.getAttribute('pattern-invalid-message');

​

            if (invalidMessage) {

                event.target.setCustomValidity(invalidMessage);

            }

        }

    })

</script>