Do we all keep the most expensive photo - why?

I expect for us older players it's conditioning. Higher price equaled a better environment /room score, as you already mentioned, and back in the day every little bit helped. Same as I used to catch me at omitting sinks when furnishing bathrooms or using no handwashing mods, because "toilet - enforced sink use - shower" was inefficient compared to just "toilet - shower". On the upside I think I've succesfully trained myself out of building for optimal routing and short distances.