Nearly all the "online storefront" options I've seen as SaaS and paid for. Think about it, there's a lot of integration and work necessary and you're paying a small fee for all that good work.
You can always stand up your own, but it take some work. I've sold a lot of gear online via my 100% static website, leveraging manual messaging and wallet payments. That's easy, but it's not saleable and isn't able to take people's orders online. So, everything is a tradeoff.
Quite a few folks here sell online using bitcoin only store fronts and are very successful. Does that help at all..?