AI products with a Product-Led Growth motion face a fundamental flaw in their unit economics. Customers expect predictable SaaS-like pricing (e.g., $20/month), but the company's costs are usage-based. This creates an inverse relationship where higher user engagement leads directly to lower or negative margins.

Unlike traditional SaaS, achieving product-market fit in AI is not enough for survival. The high and variable costs of model inference mean that as usage grows, companies can scale directly into unprofitability. This makes developing cost-efficient infrastructure a critical moat and survival strategy, not just an optimization.

AI development isn't free; it shifts the economic model of software from zero marginal cost to one with variable costs based on token consumption. This makes Cost of Goods Sold (COGS) a critical, and often new, metric for SaaS founders.

Traditional SaaS models benefited from near-zero costs for new users. AI's high computational and token costs upend this, creating deeply unprofitable users and workflows unless firms carefully manage implementation and pricing.

Unlike traditional software's zero marginal costs, AI-powered apps incur significant inference expenses that scale with users. One founder estimated needing $25M just for 100k monthly actives, challenging the classic VC model for consumer startups.

Unlike traditional SaaS, achieving product-market fit in AI doesn't guarantee a viable business. The high cost of goods sold (COGS) from model inference can exceed revenue, causing companies to lose more money as they scale. This forces a focus on economical model deployment from day one.

Mature B2B SaaS companies, after achieving profitability, now face a new crisis: funding expensive AI agents to stay competitive. They must spend millions on inference to match venture-backed startups, creating a dilemma that could lead to their demise despite having a solid underlying business.

The traditional SaaS model—high R&D/sales costs, low COGS—is being inverted. AI makes building software cheap but running it expensive due to high inference costs (COGS). This threatens profitability, as companies now face high customer acquisition costs AND high costs of goods sold.

Unlike SaaS, where infrastructure costs were commoditized, AI startups face massive, variable inference costs. This creates a new challenge where achieving product-market fit can lead to unsustainable expenses and failure, separating PMF from business durability.