So not just tempura, but any time-intensive food. My partner and I have been trying to eat out less and make more food ourselves (partially due to reading The Omnivore's Dilemma, partially due to our recent decision to stop eating fish, and partially due to the crappy economy). This has led us to baking our own bread and frying our own vegetable tempura last night.
While homebaked french bread is worth the effort, the hours one must tend to the dough (granted, lots of time it's just sitting there rising) is a bit much. I'm sure you could just let the dough rise once, and do it overnight or something, but it's not the easiest thing to make time for.
Additionally, if you don't have a big deep-frying machine, or are willing to keep a pot filled with oil, just cooking the damn tempura takes a while. I think we spent maybe an hour or so just battering and frying the veggies.
So I'm sure maybe we could have been more efficient, but I'm really thankful that we have the privilege to be able to take our time and really cook for ourselves. I'm sure there are tons of other dishes (especially if you eat meat) that take waaaay longer to prepare/simmer/cook/etc. However, when you figure that fast food is cheaper and faster, I'm sure having a homecooked (usually more healthy, although with tempura this is a bit hazy) meal is a luxury unaffordable to many.