Aside from the Cellar, which is well worth the 100,000G investment might I add, you also get some other great additions to your home along the way. The first upgrade offers players a kitchen that allows you to make recipes that replenish your energy and health, not to mention the buffs that they can offer. Then you have the second upgrade, which includes a nursery and allows players to start a family. As you might have seen in my recent Stardew Valley Children Guide, this isn't the deepest mechanic within the game, but it is needed for an achievement, so again, worth doing. Then, in addition to all of that, you get a done more space for storage and decorating. So overall, plenty of reasons to upgrade your house outside of just the Cellar.