In cognitive psychology and decision theory, loss aversion refers to people's tendency to prefer avoiding losses to acquiring equivalent gains: it is better to not lose $5 than to find $5. The principle is very prominent in the domain of economics. What distinguishes loss aversion from risk aversion is that the utility of a monetary payoff depends on what was previously experienced or was expected to happen. Some studies have suggested that losses are twice as powerful, psychologically, as gains. Loss aversion was first identified by Amos Tversky and Daniel Kahneman.Also see wikipedia on the status quo effect, which includes this: " Loss aversion, therefore, cannot wholly explain the status quo bias, with other potential causes including regret avoidance, transaction costs and psychological commitment."
I wonder whether part of the effect is the narrative difference between what you have and what you might get. The latter is naked, so to speak. It has no history, no web of memories, no particular narrative. What you have, whether it's a coffee cup or whatever, is clothed with a past, with a skein of memories, a place in a narrative.