Userscripts.org

you can use this script to find items.

ordering them by price is up to you

an example of using this script to find the lowest price would be:

function getLowestPrices(item, attempts, callback)
{
	(function recursive(items, e, h, m, item, attempts, callback, list)	// creates an recursive function to keep an search after another
	{
		list.push.apply(list, items);

		if (--attempts < 0)	// done!
		{
			callback(list.sort(function(a, b)
			{
				return ( a.Price == b.Price ? 0 : ( a.Price < b.Price ? -1 : 1 ) );
			}));
		}
		else	// keep searching...
		{
			setTimeout(Wizard.find, 1000, item, recursive, item, attempts, callback, list);
		}
	})([], undefined, false, undefined, item, attempts, callback, []);
}

// and then...
getLowestPrices("plain omelette", 10, function(items)
{
	alert("Lowest price: "+items[0].Price);
});

I haven't tested it but you got the ideia