what are the advantages of shopify?

i see a lot of people here talked about shopify. i wonder what the advantages of shopify over other e-commerce platforms (some of which are free), for example, magento, bigcommerce, vendio, zen cart, etc.

according to what i see, shopify costs $29 a month, and you have to pay a percentage every time you make a sale? you pay for your own domain, except that shopify hosts for you? shared hosting though only costs a few bucks. shared hosting usually comes with some ugly looking SSL, i dont…

what are the advantages of shopify?