I am not a realtor, so I can't speak to the actual price/value decrease nor should my answer below be taken as expert advice, but as a fellow homeowner and someone who currently has our house listed for sale, I can tell you that a "bedroom" without a closet and a window in it is not considered a legal conforming "bedroom". While most people would still consider and use it as a bedroom even without a closet, this space can not be legally called a bedroom on the assessment records. So, I would guess that it might decrease the value of the house a bit just because you include it in the listing as an actual bedroom, but I believe most people title such a space as a "flex" or "office" space. The good news is that it is still finished square footage and that is what most buyers would consider important. The bottom line is that it still has the potential to be a legal bedroom without requiring a lot of work since framing in a "small closet" would be no big deal. Hope this info helps you even just a little bit?