The sims mobile - Sell objects

We want to "upgrade" our items to the next best shower or toilet or sofa to complete a Home Collection for points, but the game forces you to keep your old toilet and shower and old sofa (that continues to mysteriously break every 3 days) in your inventory...Tell me how that makes sense. There is no motherload cheat in the mobile game, as far as I know, so we spend our Sims hard earned Simoleons on these items therefore we should be allowed to sell back the old junk for at least partial credit!