If I were to spend $300k renovating my home, the value would increase by approximately $100k.
The only real increase in home value comes from additions which add bedrooms. If I were to spend money converting an attic, a basement, or adding an add-on, I'd probably come out even at the sale.
And renovations are quickly depreciating assets. I'm much better off doing that right before a sale. A new dishwasher will be an old dishwasher before too long.