Hourly billing makes effort the visible metric, so every change request becomes a budget renegotiation and every invoice becomes a discussion of timesheets rather than business value. Selleris uses fixed-price implementation at the task level: each task is sized for a single sprint, priced once at estimate, and approved on its expected ROI before work begins. Estimation variance is absorbed by Selleris, not passed to the client. New requirements don't trigger budget escalations — they enter the same intake-and-approval loop as new tasks with their own ROI.