If you're building something you plan on throwing away, or won't be around to maintain, it makes perfect sense to throw things together quickly. If you're building something that will be a foundation for many future projects, however, it's worthwhile to put more thought, and thus more time, into building it.
> It's not your time that's being wasted
More frequently than I would like, I find myself putting a band-aid fix on something that I should have spent more time thinking through up-front. In this case it's future-me whose time I wasted by not taking my time initially.