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Define $C_{\mathrm{dev}}$ as the fixed, per-release engineering and QA cost of producing and validating the device-tier variant matrix described above — the harness time, the pass/fail sign-off per tier, per quantization scheme, per chip target. Define U as the cost of distributing model updates to the installed fleet, expanded in the next section. Define $c_{d}$ as the marginal cost of one additional on-device inference and $c_{\mathrm{cloud}}$ as the marginal cost of one additional cloud-served inference of the same model. Total cost over Q queries under each placement is

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