[devote]

<td><input class="digits6" type="text" id="count_price_disc[1]" value="100" readonly> руб.</td>
<td><input class="digits6" type="text" id="count_price_disc[8]" value="555" readonly> руб.</td>
<td><input class="digits6" type="text" id="count_price_disc[22]" value="600" readonly> руб.</td>
<script type="text/javascript">
    var total_price = 0,
        els = document.getElementsByTagName( 'input' );

    for( var el, i = 0; el = els[ i++ ]; ) {
        if ( /^count_price_disc/.test( el.id ) ) {
            total_price += Number( el.value );
        }
    }

    alert( total_price );
</script>