The ecommerce system we use is good for tens of thousands of products or just one product. Products can have variations, e.g. colours and sizes and also variations with different prices.
There are options for Australia Postal rates for different weights and standard or express post.
Payment options can include Credit Card, PayPal, Bank Transfer or Cheque.
See various ecommerce examples:
www.discountsoftwareaustralia.com (in progress)
These are all built using WordPress with the WooCommerce plugins