The very day I ordered my Dell, I ordered a Macbook Air for my wife which shipped in 2 days.
The last time I ordered a customised Macbook, delivery took weeks (and was from China). This was some years ago though, so may no longer be accurate.
Seems the answer here would be for Dell to have 'off the shelf' laptops with standard configurations they can ship quickly. If they don't already, I'm kind of amazed.