Manufacturing millions of roughly the same thing is a lot different than constructing millions of roughly one offs.
Site prep has unknown unknowns, as each site is different. Maybe there's an unexpected geologic condition, maybe the utilities won't connect without a fight, maybe the jurisdiction issues a building moratorium at the last minute. Most construction jobs won't get guaranteed pricing on materials, so any delay can change those prices, and then the client may prefer to change materials and then you may need different labor, etc.
Remodelling is full of even more unknown unknowns. Residential construction doesn't tend to have as-built drawings, and the design drawings, if available, may not have much connection to the structure as built. When you open up the walls and find surprises, that's going to increase costs.
Construction quotes are generally for no delay, no suprises, no changes. Good quotes will also include estimates in case of likely surprises, and how delay costs will be allocated and change costs and procedures.
Site prep has unknown unknowns, as each site is different. Maybe there's an unexpected geologic condition, maybe the utilities won't connect without a fight, maybe the jurisdiction issues a building moratorium at the last minute. Most construction jobs won't get guaranteed pricing on materials, so any delay can change those prices, and then the client may prefer to change materials and then you may need different labor, etc.
Remodelling is full of even more unknown unknowns. Residential construction doesn't tend to have as-built drawings, and the design drawings, if available, may not have much connection to the structure as built. When you open up the walls and find surprises, that's going to increase costs.
Construction quotes are generally for no delay, no suprises, no changes. Good quotes will also include estimates in case of likely surprises, and how delay costs will be allocated and change costs and procedures.