The rental is fine for one offs, but if you're constantly doing home improvement projects or have a hobby that requires this sort of trip, then you're doubling the trips you make to the supply store.
Also, HD is not the only place I buy supplies. Sometimes I drive an hour one way to get supplies at a rate _far_ better than HD.
And one step up from that, full truckload delivery is often $75-150, and sometimes even comes with a forklift. Often you can get it thrown in free if the order is large enough.