The "ideal" number depends heavily on the material and weave you prefer: The Ultimate Luxury Sheet Thread Count Guide - Yves Delorme

To find the best sheets, focus on the "sweet spot" of . While marketing often pushes numbers above 800 as the pinnacle of luxury, anything beyond 600 is usually achieved through misleading "multi-ply" counting methods that can actually result in heavier, less breathable fabric. The Recommended Thread Count Ranges