Upgrading to 32GB RAM is $400 and upgrading to 512GB SSD is $200, for a total of $1199.
Simply buying two Mac mini is, of course, $1198. So I guess the value of the rest of the machine is ‑$1.
Here's another angle. Think about how much value Apple places on 1 new Apple ID vs. 2 new Apple IDs. Each Apple ID is an opportunity for them to get your telemetry data, train an AI models, license software, and sell services. Apple understands that a double-capacity Mac is less likely to produce as much App Store profits as two half capacity Macs. The App Store is the most profitable part of their business.
They've correctly bet that local storage just gets eaten up by personal data rather than additional apps. More apps leads to more bloat, which hurts the user experience. Apple would rather you keep all that data in a cloud. Expensive local storage drives consumers in that direction.
They'd also rather you not own data at all. More and more of what can be consumed is rendered as a service, rented, or licensed on some temporary/conditional basis. Whatever data you really do own gets to go live in iCloud, where they can capitalize on it in some "privacy preserving" way while also charging you for it. You also won't be able to move it out, unless you're in the EU.