Notice to all matron mothers:
Walls and doors and windows are not free! You need count them in your house creation somehow. If no door components are listed some rough measure I assume there is no doors but merely entrance holes which allows pass through the room (enjoy the breeze?). Anyways as underground any wall made from stone or masonry costs -20% less than normal. Consider price of the wood I presume both exterior and interior walls are made from stone.
So, easy formula count how much your walls cost (not counting free standing walls which form barricade around your house) is this; reinforced masonry wall is 4,000gp as I recall and cost is multiplied by number of spaces you have purchased with room components. So a manor with space 10 who wants reinforced masonry walls both exterior or interior walls cost 40,000gp.
However I think the merely smoother and higher quality masonry (just a 3,000gp x per space) is good wall option also. Not as though as reinforced wall (which could be exterior wall or freestanding wall) but it's cheaper and looks nicer in smooth polish.
Doors now costs 50-200gp depending how strong 'wood' they are done from but considering lack of wood I would say you get 50% discount to any metal doors (+100% for any wood doors) as drows can mine and work with more regularly with metal than wood. Or you can do fancy force wall doors if you prefer
. Just costs 40,000gp or so.