How Much Does AI Development Actually Cost?
The number swings enormously based on one question: does this feature use an existing AI model, or does it need one trained from scratch?
AI development cost estimates vary wildly because "AI feature" describes projects with completely different scopes — from a weekend integration to a multi-month effort. The single biggest cost driver is whether the project uses an existing AI model or needs something trained from scratch.
Using an existing model is the cheaper, faster path — and the right one most of the time
Most business AI features (drafting text, classifying support tickets, summarizing documents, powering a chatbot) are built on top of an existing large language model via an API, not a custom-trained model. The engineering cost here is in the integration — prompt design, connecting the model to your real data (see retrieval-augmented generation), handling edge cases, and building the surrounding product experience, not training a model.
Custom-trained models are a different, much larger scope
Training a model from scratch (or fine-tuning one on proprietary data) is warranted only for specific, high-value problems that existing models genuinely don't handle well — and it requires real data preparation work, ongoing retraining as data changes, and specialized expertise. This is a meaningfully larger and more expensive undertaking than an API-based integration, and most businesses evaluating "AI development cost" don't actually need this path.
The ongoing cost most estimates forget
Unlike most software, an AI feature built on a hosted model has a real, usage-based ongoing cost (API calls, tokens processed) that scales with how much the feature is actually used — this isn't a one-time development cost, and it's worth estimating alongside the build cost, especially for a feature expected to see heavy use.
The most useful starting question isn't "how much does AI cost" in the abstract — it's "what specific business problem is this solving, and does it need a model at all, or would a simpler rules-based approach solve it for a fraction of the cost."