The short answer
Astra negotiates vendor rates by combining usage leverage, competitive benchmarks, and a credible BATNA — then writing the email. She pulls your last 6 months of spend from Brex or QuickBooks, ranks vendors by annual cost, and for the top 5 she gathers: your actual usage vs contracted limits, public pricing of 2-3 alternatives, and any expansion or renewal happening in the next 90 days. She drafts a per-vendor negotiation email opening with relationship value, citing specific competitive pricing, asking for a defined ask (15% off, locked rate for 24 months, removed minimum), and offering a tradeoff (longer term, case study, referral). She sends, tracks reply, and runs 1-2 rounds of back-and-forth before either landing the discount or recommending you switch. Typical recovery: 15-30% on at least 3 of 5 vendors.