[JLuterek]

It's worth considering a composable commerce SaaS. Many let you pick and choose the pieces you need, so you can fill out the remaining components and only replace what you built if their version brings significant value.

At this point, the answer is always buy and then build later if necessary. Just as we once questioned building a server vs using the cloud, using pre-built flexible components gets you to market faster.

Just be careful as the market right now has many monoliths and old systems claiming to be "headless" and "composable", but in reality Magento, Salesforce, Oracle, etc. are all expensive to work with and should only be considered for basic needs.

Looking at a marketplace you can consider marketplace specific vendors like mirakl and convictional, but being niche they can be very expensive. I would instead look at composable commerce solutions that are very flexible and can meet your marketplace needs.