Just tested this on the playground and observed that the following does work:

    "price_in_€": 42

Or were you already aware of that and lamenting that KSON requires quoting in this case, compared to YAML which doesn't?

Was lamenting the bare IDs' limitation, quoting is bad here since there is no ambiguity to resolve, no type to signal. All these new improved formats should strive to limit the bad parts of existing languages, not eliminate the goods ones