For a single embedded Python dev the math runs different from a multi-engineer platform build. One developer on a 4-month FastAPI service rebuild = 640 hours at $85/hr ≈ $54,400. Compare against an ML/DS agency retainer at $18k/month for the same scope (~$72k all-in) or a US in-house Python hire at $220k loaded plus an 8–10 week sourcing window. Solo embed wins decisively for one-service scope — a single FastAPI rewrite, a Django app upgrade, or a one-model serving layer — under 5 months. Once the work expands to multi-service ML platforms, feature stores, or a dedicated MLOps rotation, the multi-developer engagement is the right tier instead.