This system is very efficient because the potential customers are not doing general browsing. They are potential sales leads as they are already searching for a specific product that you sell, this means that if your product is competitively priced and they feel comfortable with the product and sales terms and conditions your provide, with a high level of probability the visitor will turn into a sale.
Google Shopping prices can vary on many factors, but the main factors will be: the price of the product you sell, the category of the product you sell, the target geographical location you want you adverts to appears and above all the existing demand from other Google Shopping retailers have on the same product you sell.
Geo-Targeting customers geographically is a great option offered by Google Shopping, you can target potential buyers based on their location. This can also be used to promote your business locally and offer additional services like free local delivery. There are many ways to use Geo-Targeting at your advantage.