You have a website and a host, why not just run eCommerce within WordPress and save money?
The real question is why would you want to risk liability of a breach of PII or PCI compliance when someone will handle that for you for a small monthly fee?
Shopify has risin to the top of the heap when it comes to easily managed and maintained eCommerce for most users needs. It is a walled garden, which means security is tight and they control what can and cannot be run on their servers.
You want that.
We feel that far outweighs any liability you might undertake trying to save a buck.
We can link eCommerce to your existing site or build completely within Shopify. There are advantages and disadvantages to both. We can help you with that decision.