Shopify Basic costs $29 per month. Standard Shopify costs $79 per month and their advanced service is $299 per month. This includes monthly hosting of your online store too.
Shopify offers it's own payment gateway as well as Paypal. Perfect if you don't already have a payment gateway set up. If you'd prefer to use your own payment gateway, Shopify integrates with many external providers such as Sagepay, Worldpay First Data and many more.
On Shopify Basic, using Shopify's payment gateway will cost you 2.2% + 20p per transaction. Using your own payment gateway will cost you 2% of the transaction fee.
Shopify offers basic import and export functionality via CSV. Whilst importing and updating product data is possible via CSV, we'd recommend using a verified Shopify app that allows you to import additional fields such as product attributes etc.
Shopify offers 100s of out of the box themes to choose from. Whilst your chosen theme may offer everything you need it to do, you may find it requires some customisation as well. If you need to make changes in a theme that cannot me made within the theme settings, Shopify allows you to fully customise theme template and CSS files to truly make a theme your own.
As Shopify is a Software as a Service (SAAS) provider, they will host and maintain your online store (included in your monthly fee). It's not possible to host a Shopify website on your own server.
As Shopify host your online store, they are also responsible for maintaining your site and ensuring it is kept up-to-date. This is included in the monthly Shopify fee, and it relieves site owners of the burden of having to keep websites constantly up to date.