I tried using memoize for this as well, but as you mentioned the memory bloat might negate the benefit.
I think this is a fairly common mistake in redux, to create selectors that return something new each time. Either new arrays or new objects that group certain state properties together. In those cases it is probably a good idea to reach for reselect, or consider other ways of storing the state.
Fairly certain there are a lot of connected components out there which update way too often, which is a shame :)