[alshinkareff]

$(document).ready(function() {
	
	//Таблица1
	$("#tableSelect").change(function() {
		var totalSum = 0;
		var sum;
		
		$("input[id^='pos'], select[id^='pos']").each(function() {
			var idElement = "#"+$(this).attr("id"), //Получаем id элемента
				priceField = parseInt($(idElement+"_price").text()), //Стоимость позиции
				countField = parseInt($(this).val()); //значение элемента
			
			$(idElement+"_count").text(priceField * countField); //Выводим сумму по позиции
			totalSum += priceField * countField;
		});
		$("#count_price span").text(totalSum);
		sum = totalSum1 + totalSum2 + totalSum3 + totalSum4;
	});
	
	
	//Таблица2
	$("#tableSelect2").change(function() {
		var totalSum = 0;
		var sum;
		
		$("input[id^='pos2'], select[id^='pos2']").each(function() {
			var idElement = "#"+$(this).attr("id"),
				priceField = parseInt($(idElement+"_price").text()),
				countField = parseInt($(this).val());
			
			$(idElement+"_count").text(priceField * countField);
			totalSum += priceField * countField;
		});
		$("#count_price2 span").text(totalSum);
		sum = totalSum1 + totalSum2 + totalSum3 + totalSum4;
	});

		
	//Таблица3
	$("#tableSelect3").change(function() {
		var totalSum = 0;
		var sum;
		
		$("input[id^='pos3'], select[id^='pos3']").each(function() {
			var idElement = "#"+$(this).attr("id"),
				priceField = parseInt($(idElement+"_price").text()),
				countField = parseInt($(this).val()); 
			
			$(idElement+"_count").text(priceField * countField); 
			totalSum += priceField * countField;
		});
		$("#count_price3 span").text(totalSum);
		sum = totalSum1 + totalSum2 + totalSum3 + totalSum4;
	});
	
	
	//Таблица4
	$("#tableSelect4").change(function() {
		var totalSum = 0;
		var sum;
		
		$("input[id^='pos4'], select[id^='pos4']").each(function() {
			var idElement = "#"+$(this).attr("id"),
				priceField = parseInt($(idElement+"_price").text()),
				countField = parseInt($(this).val());
			
			$(idElement+"_count").text(priceField * countField);
			totalSum += priceField * countField;
		});
		$("#count_price4 span").text(totalSum);
		sum = totalSum1 + totalSum2 + totalSum3 + totalSum4;
	});
	
	var sum = 0;
	var totalSum1 = parseInt($(#"count_price span").text());
	var totalSum2 = parseInt($(#"count_price2 span").text());
	var totalSum3 = parseInt($(#"count_price3 span").text());
	var totalSum4 = parseInt($(#"count_price4 span").text());

	sum = totalSum1 + totalSum2 + totalSum3 + totalSum4;
	
	$("#sum span").text(sum); 
	
});

Ну и к HTML добавлен <div id="sum">ОБЩЕЕ ИТОГО<span></span></div>