Like in the case of cars,  where you have cars from $1800 – $million. E-commerce solutions come in all shapes and sizes.
Though for many companies, the choice is entirely not within their domain of understanding, it helps to know the basics of it.

Frugal Solutions

WordPress – Woo-Commerce
I start with WordPress first. Considering the fact that 20% of the Web runs on wordpress, it is only logical that someone came up with the e-Commerce functionality pluging for this blogging platform. There are many choices here, but woo-commerce seems to be most stable and widely supported pluging.
This helps small business owners; with say less than a million dollars revenue to quickly set up an online shop, generally less than 10 days including the payment gateway integration.

Offers most basic shopping functionality, more suitable for 1-2 person managed sites.

This is also assuming that the customer has some basic understanding of domain, hosting, renewal, cpanel plesk etc…

Shopify
For someone who does not want to get into the hassle of hosting, configuring etc… The cheapest hosted e-commerce solution comes in the form of shopify. No worry about having to maintain site security, scaling issues etc…
Since this is hosted on the cloud, you can scale comfortably. More suited for simple business with no complex supply chain.
Unlike wordpress, you can’t build custom add-ons over the website. This severelly restricts this as the choice when some business complexity arises. Simple things like, you want to restrict shipping to some zip codes cannot be done. And you can’t write an add-on to do this function like in the case of wordpress. Their plan starts at $19 per month which is a great bargain for getting online with a store. Payment gateway options are restricted and in-built which may be convenient is some case but not so for business wanting to use their own banking gateway for other reasons.

Template options are available, but gets limited once you are a serious online business owner wanting to do some serious juggling of components and layouts.

Good for customers who never want to have an in-house Web management team.

If you decide to migrate, though you can take a data dump, I am always concerned about the Google impact.

More to come here:
Hybris
Demandware
Websphere