The second paragraph above is the one that is the real driver to the cost of owning a larger boat. As someone who not long ago stepped up from a J/30 to a J/40, I can relate to the OP's question. it's not merely that fittings get bigger with increasing size/load, It's that the number and complexity of systems goes through the roof. Taking the fresh water system as an example, on the J/30 there's a single 24 gallon water tank, with a manual foot-operated cold-water pump in the galley, and a hand-pump in the head. That's it. If you wanted warm water you used a solar shower, or boiled water on the stove. On the J/40, there are 3 tanks totaling over 120 gallons, an electric pressure pump, a water heater, an accumulator, 4 hot/cold faucets (1 in each head, 1 for the galley, and a cockpit shower), along with a city water inlet and a tank selector valve manifold, plus all the tubing to hook up all the necessary connections. And with winter approaching, what was a 15 minute job to winterize on the J/30 now is multiple times longer on the J/40.