For a very cost effective solution I recommend the following ECommerce shopping carts:
Virtuemart and Zen Cart, these are both open source applications with great products and regular updates. They will process an order and email the customer a receipt and email the vendor a notice that a order has been placed. The vendor then log's in to their account and retrieves the transaction details and processes the order.
Setup fee AU$ 4500.00 (to integrate the shopping cart into your website and to customize the appearance)
Optional extras like a about the company, press releases, product demonstrations, newsletter system and anything else you require can also be added onto the site.
Monthly Fees AU$ 0.00
SSL certificate will be required by your bank or payment processor if you are processing credit cards.
Offline credit card processing (using your normal credit card processing machine) is also ossible.