1,use prototype overwriting Product.Options.prototype.reloadPrice

Product.Options.prototype.oldReloadPrice = Product.Options.prototype.reloadPrice;
Product.Options.prototype.reloadPrice = function(){
    this.oldReloadPrice();
    var currentPrice = howToGetThePrice();
    doSomethingWithTheCurrentPrice(currentPrice);
};

2,use jQuery get the current price by cleaning the html inside an span

function getCurrentPrice(){
    var ds = optionsPrice.priceFormat.decimalSymbol,
    gs =optionsPrice.priceFormat.groupSymbol,
    pf=optionsPrice.priceFormat.pattern;

    var price = 0;
    jQuery('#product-price-<?php echo $_product->getId() ?>_clone span')
        .html()
        .replace(new RegExp("\\"+gs,'g'),'')
        .replace(new RegExp("\\"+ds,'g'),'.')
        .sub(/([0-9\.\,]+)/,function(matches){
            price = parseFloat(matches[1]);
    });
    return price;
}

3,Update element value with this code，you can update total price with qty.

$('totalPrice').innerHTML = currentPrice * $('qty').value