Use Shopify for selling web tools or services

Shopify is suitable for selling online services, tools or not? Is it possible to use Shopify in the same way as PayPal or any other payment processor, for example simple purchase flow:

• 1) user clicks the 'Buy' button,
• 2) page navigates to the Shopify product page where user has to pay (commit the purchase)
• 3) redirects back to the website with purchase confirmation and token - which is used to link it to the buyer (user that clicked the Buy button).

this should be common and pretty simple, though I couldn't find any tutorial or sample

Yes, it's possible.

Create a store, set up a payment processor, create a product that is (a service, a tool or whatever you want to sell) and you're ready to go.

Also, read bout selling services.