For simple shopping cart solutions we a robust Content Management System called Drupal. This is a shareware program that is free to install, so you are only paying for timein your development. Basic installation $800. Add-ons and customizations more.
Samples
ArtRoundup.com: Hamilton Montana site for selling beautiful antiques and home furnishings.
Besthealthoil.com: This site was created as a search engine optimization tool. It is using blog technology to create useful information about the topic of quality Omega=3 vegetable oil. It gained page one recognition within weeks.
peaceworkspubs.com: Internation organization which sells books and tapes online.
SpincraftPatterns.com: Original knitting patterns. The product on this site is downloaded automatically after purchase.
KnittingZone.com: Sells knitting supplies throughout the country.
Wingnutcomic.com: Traveling comedian... be sure to watch his clips. He's funny! He will soon be selling t-shirts and other products online.
These sites have an extensive back end shopping cart. Merchant accounts can be managed through your already established bank account (if you take credit cards in your store), or run through PayPal, or a service like Authorize.net on the web.
These sites have modules for sending customer newsletters, uploading products, receiving orders, and managing customers.