It all depends on the vendor and how much you are replacing. To fully furnish (furniture and decor) a budget-friendly room I would budget between $5-8k, for mid-range $8-15k and high-end $15k+. These of course are estimates and depend on the exact room type.
Budget-friendly Vendors could include- IKEA, Walmart, Target, Amazon, Wayfair etc
Mid-Range Vendors could include- West Elm, Crate & Barrel, Anthropologie, Article, Four Hands etc
High-End Vendors could include- Design Within Reach, Visual Comfort, 1st Dibs, Restoration Hardware, Jonathan Adler etc