How much does UI/UX design cost?

Per-screen and per-project pricing suit different jobs. Per-screen is transparent and fair for a defined set of pages, so you know exactly what each extra screen adds. Project (fixed-fee) pricing works better when the flows are complex or exploratory — research, multiple concepts, and revision rounds are hard to bill cleanly by the screen, so a scoped project fee avoids nickel-and-diming.

What affects the cost: the number of unique screens and states, whether you need user research and usability testing, prototype fidelity (static mockups vs clickable prototypes), responsive and multi-platform versions, how many revision rounds are included, and whether you want a reusable design system rather than one-off screens.

Honestly, the cheapest 'pretty mockups' are often the most expensive in the end. Design without research or developer-ready handoff gets rebuilt during development, and that rework costs more than doing it properly once. Good UX pays back through higher conversion, so judge quotes on process and handoff quality, not just the headline number.