<script type="text/javascript">
function calc() {
var operations = document.getElementById("operations");
var workers = document.getElementById("workers");
var system = document.getElementById("system");
var result = document.getElementById("operations");
var result = document.getElementById("workers");
var result = document.getElementById("result_system");
var result = document.getElementById("result");
var price_operations = 0;
var price_workers = 0;
var price_system = 0;
var price = 0;
price_operations += parseInt(operations.value)*2;
price_workers += parseInt(workers.value)*3;
price_system += parseInt(system.options[system.selectedIndex].value);
result_operations.innerHTML = price_operations;
result_workers.innerHTML = price_workers;
result_system.innerHTML = price_system;
price=price_operations + price_workers;
result.innerHTML = price;
}
</script>
<table>
<tr>
<td width="100"><input type="text" id="operations" value="0" onchange="calc()" /></td>
<td width="200"><span id="result_operations">0</span></td>
</tr>
<tr>
<td width="100"><input type="text" id="workers" value="0" onchange="calc()" /></td>
<td width="200"><span id="result_workers">0</span></td>
</tr>
<tr>
<td width="250" class="td_result">ИТОГО:</td>
<td class="td_result"><span id="result">0</span></td>
</tr>
<tr>
<td width="100">
<select onchange="calc()" id="system">
<option value="">Не выбрано</option>
<option value="0">1</option>
<option value="1">2</option>
<option value="2">3</option>
<option value="3">4</option>
<option value="4">5</option>
</select>
</td>
<td width="200"><span id="result_system">0</span></td>
</tr>
</table>
<table>
<tr>
<td></td><td>1</td><td>2</td><td>3</td><td>4</td><td>5</td>
</tr>
<tr>
<td>0-3</td><td>100</td><td>200</td><td>300</td><td>400</td><td>500</td>
</tr>
<tr>
<td>4-10</td><td>600</td><td>700</td><td>800</td><td>900</td><td>1000</td>
</tr>
<tr>
<td>11-30</td><td>1100</td><td>1200</td><td>1300</td><td>1400</td><td>1500</td>
</tr>
<tr>
<td>31-50</td><td>1600</td><td>1700</td><td>1800</td><td>1900</td><td>2000</td>
</tr>
<tr>
<td>51-100</td><td>2100</td><td>2200</td><td>2300</td><td>2400</td><td>2500</td>
</tr>
<tr>
<td>>100</td><td>100</td>
</tr>
</table>
var selected_column = 0; //выбранный столбец из списка
var row_index = 0; //индекс строки
if(value > 0 && value < 4)
{
row_index = 1;
}elseif(value > 3 && value < 11){
row_index = 2;
}
...
var table = document.getElementsByTagName('table'); // получаем таблицы
var rows = table[1].getElementsByTagName('tr'); //выбираем все строки нужной таблицы(у вас их две, выбираем вторую(индекс начинается с 0)) данной таблицы
var columns = rows[4].getElementsByTagName('td'); //выбираем столбцы нужной строки, тут вводим индекс полученный после if/else
alert(columns[4].textContent); //и наконец получаем значение, тут вводим индекс выбранного столбца