Kitchen budgets fail in predictable places, and almost never on the tile. They fail on cabinet allowances that were set before anyone priced real cabinets, on plumbing and electrical that had to move once the walls were open, and on changes made mid-project.
Cabinets are usually the single largest line, and the range is enormous. Stock cabinets, semi-custom, and fully custom built to your kitchen can differ by a factor of three for the same layout. Decide early which one you're buying and price the estimate against it.
Countertops, appliances, and labor make up most of the rest. Labor covers demo, rough-in, drywall, cabinet installation, counter templating and install, backsplash, flooring, trim, and paint. When one crew does all of it, the schedule holds together and there's no gap between trades where a kitchen sits half-finished.
Keep a contingency of ten to fifteen percent for what's behind the walls, especially in Portland-area homes built before 1980. And make every change a written estimate before it becomes work, so the final invoice is never a surprise.