Emdashes and commas aren't interchangeable, and your example there demonstrates one great reason why. The emdash establishes a discontinuity rather than one thing flowing into another, which is why the tomatoes don't merit one but the Ferrari does: you are using the emdash to emphasize the situational irony.

Going back to Anthropic's post:

> They’re the world’s most advanced models for coding and knowledge work---and their research capabilities offer an early glimpse of how AI models will contribute to scientific progress.

The first thing directly implies and flows smoothly into the next---or would, if not for the awkward emdash. There is no discontinuity, no twist or shift in context, no implied question and provided answer, no punchline. It's just distracting.

Your first example shouldn't have a comma at all.