Ada

Pricing model: Usage-based / pay-as-you-go (conversation-based pricing; Ada describes "simple, usage-based pricing" on its pricing page). Public list prices: Not published on Ada's official site. Billing cadence & payment terms: Invoices are typically billed as annual, upfront payments by default (per Ada Customer Terms / Transaction Document). What counts as usage / examples: Pricing and overage rates reference "Conversations" and are defined in the Transaction/Order Form or Ada's then-current rates; the site does not publish per-conversation or per-user unit prices. How to purchase / get pricing: Ada requires contacting sales / booking a demo or consultation (demo/trial request pages) to receive pricing and a custom quote. Notes & conditions: Ada states it is a good fit for enterprises with ~300,000+ annual conversations; renewal fees may be subject to a 10% increase. A free trial instance can be requested via the trial/demo page (trial availability appears to be on a request basis rather than a self-serve public trial with listed duration).

Public pricing details not found on vendor site — contact Ada for a custom quote.