> WordPress + WooCommerce, PrestaShop and Magento already do that. Drop $10 to $20/month on hosting on DigitalOcean, install Wordpress, install WooCommerce, buy a cheap theme, buy whatever extra plugins you need, setup your payment system (PayPal and Stripe are supported), and you're off to the races.
My wife is starting a fashion business. This is a hill too high to climb for a non-technical user. She was up and running in 30 minutes with my credit card and Shopify earlier this week. We don't have time to maintain an instance, troubleshoot Wordpress theme and plugin incompatibilities, etc. That's time better spent on sales funnel optimizations, manufacturing product, and customer support.
Would we consider more advanced ecommerce systems? Sure, when she hits $1MM/year in annual revenue. Until then, Shopify earns their keep (and margin) by taking care of the mundane. Make dollars, don't pinch pennies.
See: "Dropbox is just ftp + git" [1]