We have been operating as an industrial packaging manufacturer in Izmir for 14 years. We want to completely overhaul our legacy web portal where our distributors place orders, track their balances, and generate quotes with custom discount tiers. A software agency we met with quoted us 185,000 TL for the entire project. However upon reviewing the proposal contract, we noticed that 50,000 TL of that amount was listed as a separate line item under "User Experience and User Interface Design (UI/UX)".
Up until now we assumed this work simply meant picking button colors or making the pages look pretty. The software agency, on the other hand, insists that coding cannot begin without this stage, or the entire process will stall. What exactly does user interface and user experience design encompass in a web software project and should it truly be billed as a separate item from development? Also if we approve this budget, what concrete deliverables should we have written into the contract?