Bring in a specialist when a missing capability blocks the next decision and the proposed engagement closes that specific gap. This is a judgement about capability and risk, not a claim that outsourcing always lowers cost.
An evaluation specialist is useful when results are close, labels are disputed or rare failures could dominate the decision. A data specialist can help when parsing, provenance or labelling is the bottleneck. An adaptation engineer becomes useful after a stable behavioural gap survives baseline improvements. An inference specialist helps when traffic, capacity or latency makes serving the main uncertainty.
Ask for evidence of a comparable task, the named people doing the work, the assumptions behind their recommendation and the artefacts you retain. A platform subscription is not the same purchase as a delivery team; neither automatically includes independent evaluation or regulatory advice. Scope counsel and security review according to the actual data and use.