So while most of the software is open source rather than proprietary, you still have a fair point that customers pay for support (as they do with most enterprise products). One could theoretically use the product without first-party software updates, managing the open source oneself... but that would have practical impediments (and runs counter to the all-in-one simplicity that customers value in the Oxide product).

Two points about your last point. First, software improvements benefit all customers; as the business grows, the effective cost per customer shrinks. Also, most customers grow their Oxide deployment or will replace hardware after a depreciation cycle. The sustainability of investments into the software (and the product generally) is on solid ground.