Generally speaking larger and more open spaces are less per square foot than smaller spaces. Building a two-story home addition is generally less per square foot than building a single story because the space shares the same roof and foundation. (Count both floors when calculating square footage of added space if second floor is to be finished or partially finished). Any portion of the existing home that is affected and/or gets remodeled (among other things) has a large impact on the total investment.
If the layout of your kitchen is essentially okay, you may only want to replace your cabinets, countertops, sink and flooring. Add a fresh coat of paint to the walls and ceiling and maybe a new tiled backsplash. Basically everything would stay close to or in the same location. Appliances not included.
Your kitchen may be in need of a more extensive renovation involving relocating some of the appliances and sink. Included in this would be a new layout design, updated electrical and lighting on existing circuitry, new cabinets, crown moulding, countertops, new flooring and paint, tiled backsplash and under cabinet lighting. Existing plaster or drywall would remain mostly intact. Appliances not included.
A complete kitchen remodeling may include extensive renovation involving completely “gutting” your kitchen; removing everything including the wall and ceiling finishes, removing some walls to “open up” the space. In addition to a new design/layout, also included would be all new electrical, lighting and plumbing within the kitchen, new wall and ceiling finishes, tile or hardwood flooring, custom cabinets and new countertops, tiled backsplash, possibly a new window or two, etc… Appliances not included.
Remove and replace all contents of an average sized, three fixture bathroom including the tub/shower unit, toilet, sink, faucet, tub/shower valve, vanity and vanity top, installing new flooring, new exhaust fan, vanity light and mirror, bathroom accessories, little or no plumbing or electrical work beyond replacing the fixtures. Everything would connect to existing plumbing in existing locations. Most of the wall and ceiling finishes would stay intact but would be freshly painted.