Correct me if I'm wrong

This blog post shows how to create a checkout URL with Shopify and pass custom variables for the entire order. I want to create a static website that can sell one product (and later maybe more). However, implementing your own online shop system seems to be quite a “let’s reinvent the wheel” task (and far from a static website) - there must be a better solution. The Buy Button from Shopify’s Light plan for 9$ per month seems fitting, so I give it a try.