Never checked that stuff before. Lightroom 5 open and sitting idle draws about 2GB. Web browsing with 3 open tabs draws under 2GB here. This system has 8Gb memory and does all I need, so far anyway.
My other one has 8Gb and I used LR, PS and anything else all the time. But depending upon what I did in LR or PS, I could suck its resources dry in no time. It would still function but I could watch the progress bar slowly crawl to 100% just like in the good old days.