jawe

<form>
<p>Cena knihy: <span id="item-price">440</span>,- Kč s DPH</p>

<input type="number" name="item-count" value="1" min="1" step="1"> <!-- selectovat přes name -->
<p>Zboží celkem: <span id="item-count-price"></span>
<br>
<input type="radio" name="delivery-option" value="(+ 99,- Kč) Dobírkou (Česká pošta)" checked>(+ 99,- Kč) Dobírkou (Česká pošta)<br>
<input type="radio" name="delivery-option" value="(+ 0,- Kč) Osobní odběr v Galerii Gottfrei, Krnovská 14/13, Opava">(+ 0,- Kč) Osobní odběr v Galerii Gottfrei, Krnovská 14/13, Opava
<p>Cena celkem: <span id="order-total"></span>,- Kč</p>
</form>

<script
  src="http://code.jquery.com/jquery-3.3.1.min.js"
  integrity="sha256-FgpCb/KJQlLNfOu91ta32o/NMZxltwRo8QtmkMRdAu8="
  crossorigin="anonymous"></script>

<script type="text/javascript">
	$(document).ready(function() {
		renderPrice();
		$("input[name=item-count]").bind('keyup input change', renderPrice);
		$("input[name=delivery-option]").change(renderPrice);
	});

	function renderPrice() {
		var subTotalPrice = getSubtotalPrice();
		var totalPrice = getTotalPrice(subTotalPrice);
		
		$("#item-count-price").text(subTotalPrice.toString());
		$("#order-total").text(totalPrice.toString());
	}

	function getSubtotalPrice() {
		var bookPrice = parseInt($("#item-price").text());
		var bookCount = parseInt($("input[name=item-count]").val())
		var normalizedBookCount = Math.max(bookCount || 0, 0);
		return bookPrice * normalizedBookCount;
	}

	function getTotalPrice(subtotalPrice) {
		var shippingPriceText = $("input[name=delivery-option]:checked").val()
		var shippingPrice = extractShippingPrice(shippingPriceText);
		return shippingPrice + subtotalPrice;
	}

	function extractShippingPrice(shippingText) {
		var defaultPrice = 0;
		var parts = shippingText.toLowerCase().match(/[0-9]+|kč/g);

		for (var i = 0; i < parts.length; i++) {
			if (parts[i] === 'kč') {
				return parseInt(parts[i - 1], 10) || defaultPrice;
			}
		}

		return defaultPrice;
	}

	function replaceAll(target, search, replacement) {
    	return target.replace(new RegExp(search, 'g'), replacement);
	};
</script>