50% probably wouldn't be enough, but I don't know that details of residential development well enough. I think that baking it on size and amenities more than cost to determine if it is reasonable might be better.
Doing a one off upgrade/remodel/rebuild is always more expensive per unit or sqft than a large development that follows variations on one design and overhead diffuses costs over many units.
Add in custom design for security, which probably includes fire suppression, gardening against attack, and security infrastructure, and you are likely much more than 50% over market per sqft of remodeled space.
But you can compare features more readily. If it has five kitchens, a grand entrance with marble columns and a double stairwell, then it's well into luxury wants and not living and hosting needs plus security.
50% probably wouldn't be enough, but I don't know that details of residential development well enough. I think that baking it on size and amenities more than cost to determine if it is reasonable might be better.
Doing a one off upgrade/remodel/rebuild is always more expensive per unit or sqft than a large development that follows variations on one design and overhead diffuses costs over many units.
Add in custom design for security, which probably includes fire suppression, gardening against attack, and security infrastructure, and you are likely much more than 50% over market per sqft of remodeled space.
But you can compare features more readily. If it has five kitchens, a grand entrance with marble columns and a double stairwell, then it's well into luxury wants and not living and hosting needs plus security.