What does this equation mean?

The marginal-cost argument for on-device inference is not wrong; it is one term in a four-term equation, and the other three — variant-matrix engineering, distillation-versus-teacher economics, and update-distribution bandwidth — are each individually documented at real, checkable magnitudes in this article. Distillation itself is nearly always worth doing: disclosed training runs in the hundreds of dollars clear their own break-even point against even modest cloud query volumes almost immediately. Placing the result on a device is a separate, harder calculation, one that rises with every additional tier a release has to validate and every device already in the field that has to receive the update whether or not it ever calls the feature. Ask which term in $Q^{*}_{\mathrm{device}}$ = ($C_{\mathrm{dev}}$ + U) / ($c_{\mathrm{cloud}}$ - $c_{d}$) a given vendor’s public statement is actually about, and whose incentive is served by leaving the other three out of the sentence.