Consumption Pricing Is Blowing Legal AI Budgets — But Cost-Per-Matter Is Falling

The Legal Stack's 2026 AI Compute Cost Shift Report found that firms that fully transitioned to consumption-based pricing from at least one major legal AI vendor saw annual AI spend increase 47.3% year-over-year — compared to 12.1% for firms on legacy seat licenses. More than 62% of respondents reported actual spend exceeded budget projections by a median of 28.4%. Despite the sticker shock, cost-per-matter data tells a different story: AI-assisted contract review produced a median cost of $340 per matter versus $890 without AI (62% reduction); regulatory research fell from $1,420 to $510 per matter; and litigation document review dropped from $11,800 to $4,200 per matter. The unit-economics case for AI remains strong — but the gap between firm-level AI spending decisions (consumption-based, open-ended) and the discipline of matter-level cost tracking is creating budget volatility that CFOs are only beginning to manage systematically.